Genome Glossary
A glossary of genetic terms. Choose terms
by using the list of links below.
-
Acquired genetic
mutation
-
See:
somatic cell genetic mutation
-
Additive genetic
effects
-
When the combined effects of alleles at different loci
are equal to the sum of their individual effects.
See also: anticipation,
complex trait
-
Adenine (A)
-
A nitrogenous base, one member of the base pair AT
(adenine-thymine).
See also: base pair,
nucleotide
-
Affected relative
pair
-
Individuals related by blood, each of whom is affected
with the same trait. Examples are affected sibling,
cousin, and avuncular pairs.
See also:
avuncular relationship
-
Aggregation
technique
-
A technique used in model organism studies in which
embryos at the 8-cell stage of development are pushed
together to yield a single embryo (used as an alternative
to microinjection).
See also:
model organisms
-
Allele
-
Alternative form of a genetic locus; a single allele for
each locus is inherited from each parent (e.g., at a
locus for eye color the allele might result in blue or
brown eyes).
See also: locus,
gene expression
-
Allogeneic
-
Variation in alleles among members of the same species.
-
Alternative splicing
-
Different ways of combining a gene's exons to make
variants of the complete protein
-
Amino
acid
-
Any of a class of 20 molecules that are combined to form
proteins in living things. The sequence of amino acids in
a protein and hence protein function are determined by
the genetic code.
-
Amplification
-
An increase in the number of copies of a specific DNA
fragment; can be in vivo or in vitro.
See also: cloning,
polymerase chain reaction
-
Animal
model
-
See: model organisms
-
Annotation
-
Adding pertinent information such as gene coded for,
amino acid sequence, or other commentary to the database
entry of raw sequence of DNA bases.
See also:
bioinformatics
-
Anticipation
-
Each generation of offspring has increased severity of a
genetic disorder; e.g., a grandchild may have earlier
onset and more severe symptoms than the parent, who had
earlier onset than the grandparent.
See also:
additive genetic effects,
complex trait
-
Antisense
-
Nucleic acid that has a sequence exactly opposite to an
mRNA molecule made by the body; binds to the mRNA
molecule to prevent a protein from being made.
See also:
transcription
-
Apoptosis
-
Programmed cell death, the body's normal method of
disposing of damaged, unwanted, or unneeded cells.
See also: cell
-
Arrayed library
-
Individual primary recombinant clones (hosted in phage,
cosmid, YAC, or other vector) that are placed in
two-dimensional arrays in microtiter dishes. Each primary
clone can be identified by the identity of the plate and
the clone location (row and column) on that plate.
Arrayed libraries of clones can be used for many
applications, including screening for a specific gene or
genomic region of interest.
See also: library,
genomic library,
gene chip technology
-
Assembly
-
Putting sequenced fragments of DNA into their correct
chromosomal positions.
-
Autoradiography
-
A technique that uses X-ray film to visualize
radioactively labeled molecules or fragments of
molecules; used in analyzing length and number of DNA
fragments after they are separated by gel
electrophoresis.
-
Autosomal dominant
-
A gene on one of the non-sex chromosomes that is always
expressed, even if only one copy is present. The chance
of passing the gene to offspring is 50% for each
pregnancy.
See also: autosome,
dominant,
gene
-
Autosome
-
A chromosome not involved in sex determination. The
diploid human genome consists of a total of 46
chromosomes: 22 pairs of autosomes, and 1 pair of sex
chromosomes (the X and Y chromosomes).
See also:
sex
chromosome
-
Avuncular
relationship
-
The genetic relationship between nieces and nephews and
their aunts and uncles.
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-
Backcross
-
A cross between an animal that is heterozygous for
alleles obtained from two parental strains and a second
animal from one of those parental strains. Also used to
describe the breeding protocol of an outcross followed by
a backcross.
See also:
model organisms
-
Bacterial
artificial chromosome (BAC)
-
A vector used to clone DNA fragments (100- to 300-kb
insert size; average, 150 kb) in Escherichia
coli cells. Based on naturally occurring F-factor
plasmid found in the bacterium E. coli.
See also:
cloning vector
-
Bacteriophage
-
See: phage
-
Base
-
One of the molecules that form DNA and RNA
molecules.
See also: nucleotide,
base
pair, base sequence
-
Base
pair (bp)
-
Two nitrogenous bases (adenine and thymine or guanine and
cytosine) held together by weak bonds. Two strands of DNA
are held together in the shape of a double helix by the
bonds between base pairs.
-
Base
sequence
-
The order of nucleotide bases in a DNA molecule;
determines structure of proteins encoded by that DNA.
-
Base sequence
analysis
-
A method, sometimes automated, for determining the base
sequence.
-
Behavioral genetics
-
The study of genes that may influence behavior.
-
Bioinformatics
-
The science of managing and analyzing biological data
using advanced computing techniques. Especially important
in analyzing genomic research data.
See also: informatics
-
Bioremediation
-
The use of biological organisms such as plants or
microbes to aid in removing hazardous substances from an
area.
-
Biotechnology
-
A set of biological techniques developed through basic
research and now applied to research and product
development. In particular, biotechnology refers to the
use by industry of recombinant DNA, cell fusion, and new
bioprocessing techniques.
-
Birth
defect
-
Any harmful trait, physical or biochemical, present at
birth, whether a result of a genetic mutation or some
other nongenetic factor.
See also: congenital,
gene,
mutation,
syndrome
-
BLAST
-
A computer program that identifies homologous (similar)
genes in different organisms, such as human, fruit fly,
or nematode.
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-
Cancer
-
Diseases in which abnormal cells divide and grow
unchecked. Cancer can spread from its original site to
other parts of the body and can be fatal.
See also:
hereditary cancer,
sporadic cancer
-
Candidate gene
-
A gene located in a chromosome region suspected of being
involved in a disease.
See also:
positional cloning,
protein
-
Capillary array
-
Gel-filled silica capillaries used to separate fragments
for DNA sequencing. The small diameter of the capillaries
permit the application of higher electric fields,
providing high speed, high throughput separations that
are significantly faster than traditional slab gels.
-
Carcinogen
-
Something which causes cancer to occur by causing changes
in a cell's DNA.
See also: mutagene
-
Carrier
-
An individual who possesses an unexpressed, recessive
trait.
-
cDNA
library
-
A collection of DNA sequences that code for genes. The
sequences are generated in the laboratory from mRNA
sequences.
See also: messenger RNA
-
Cell
-
The basic unit of any living organism that carries on the
biochemical processes of life.
See also: genome,
nucleus
-
Centimorgan (cM)
-
A unit of measure of recombination frequency. One
centimorgan is equal to a 1% chance that a marker at one
genetic locus will be separated from a marker at a second
locus due to crossing over in a single generation. In
human beings, one centimorgan is equivalent, on average,
to one million base pairs.
See also: megabase
-
Centromere
-
A specialized chromosome region to which spindle fibers
attach during cell division.
-
Chimera (pl.
chimaera)
-
An organism that contains cells or tissues with a
different genotype. These can be mutated cells of the
host organism or cells from a different organism or
species.
-
Chimeraplasty
-
An experimental targeted repair process in which a
desirable sequence of DNA is combined with RNA to form a
chimeraplast. These molecules bind selectively to the
target DNA. Once bound, the chimeraplast activates a
naturally occurring gene-correcting mechanism. Does not
use viral or other conventional gene-delivery
vectors.
See also: gene therapy,
cloning vector
-
Chloroplast
chromosome
-
Circular DNA found in the photosynthesizing organelle
(chloroplast) of plants instead of the cell nucleus where
most genetic material is located.
-
Chromomere
-
One of the serially aligned beads or granules of a
eukaryotic chromosome, resulting from local coiling of a
continuous DNA thread.
-
Chromosomal deletion
-
The loss of part of a chromosome's DNA.
-
Chromosomal
inversion
-
Chromosome segments that have been turned 180 degrees.
The gene sequence for the segment is reversed with
respect to the rest of the chromosome.
-
Chromosome
-
The self-replicating genetic structure of cells
containing the cellular DNA that bears in its nucleotide
sequence the linear array of genes. In prokaryotes,
chromosomal DNA is circular, and the entire genome is
carried on one chromosome. Eukaryotic genomes consist of
a number of chromosomes whose DNA is associated with
different kinds of proteins.
-
Chromosome painting
-
Attachment of certain fluorescent dyes to targeted parts
of the chromosome. Used as a diagnositic for particular
diseases, e.g. types of leukemia.
-
Chromosome region p
-
A designation for the short arm of a chromosome.
-
Chromosome region q
-
A designation for the long arm of a chromosome.
-
Clone
-
An exact copy made of biological material such as a DNA
segment (e.g., a gene or other region), a whole cell, or
a complete organism.
-
Clone
bank
-
See: genomic library
-
Cloning
-
Using specialized DNA technology to produce multiple,
exact copies of a single gene or other segment of DNA to
obtain enough material for further study. This process,
used by researchers in the Human Genome Project, is
referred to as cloning DNA. The resulting cloned
(copied) collections of DNA molecules are called clone
libraries. A second type of cloning exploits the natural
process of cell division to make many copies of an entire
cell. The genetic makeup of these cloned cells, called a
cell line, is identical to the original cell. A third
type of cloning produces complete, genetically identical
animals such as the famous Scottish sheep, Dolly.
See also:
cloning vector
-
Cloning vector
-
DNA molecule originating from a virus, a plasmid, or the
cell of a higher organism into which another DNA fragment
of appropriate size can be integrated without loss of the
vector's capacity for self-replication; vectors
introduce foreign DNA into host cells, where the DNA can
be reproduced in large quantities. Examples are plasmids,
cosmids, and yeast artificial chromosomes; vectors are
often recombinant molecules containing DNA sequences from
several sources.
-
Code
-
See: genetic code
-
Codominance
-
Situation in which two different alleles for a genetic
trait are both expressed.
See also:
autosomal dominant,
recessive gene
-
Codon
-
See: genetic code
-
Coisogenic or
congenic
-
Nearly identical strains of an organism; they vary at
only a single locus.
-
Comparative genomics
-
The study of human genetics by comparisons with model
organisms such as mice, the fruit fly, and the bacterium
E. coli.
-
Complementary DNA (cDNA)
-
DNA that is synthesized in the laboratory from a
messenger RNA template.
-
Complementary
sequence
-
Nucleic acid base sequence that can form a
double-stranded structure with another DNA fragment by
following base-pairing rules (A pairs with T and C with
G). The complementary sequence to GTAC for example, is
CATG.
-
Complex trait
-
Trait that has a genetic component that does not follow
strict Mendelian inheritance. May involve the interaction
of two or more genes or gene-environment
interactions.
See also:
Mendelian inheritance,
additive genetic effects
-
Computational
biology
-
See: bioinformatics
-
Confidentiality
-
In genetics, the expectation that genetic material and
the information gained from testing that material will
not be available without the donor's consent.
-
Congenital
-
Any trait present at birth, whether the result of a
genetic or nongenetic factor.
See also: birth defect
-
Conserved sequence
-
A base sequence in a DNA molecule (or an amino acid
sequence in a protein) that has remained essentially
unchanged throughout evolution.
-
Constitutive
ablation
-
Gene expression that results in cell death.
-
Contig
-
Group of cloned (copied) pieces of DNA representing
overlapping regions of a particular chromosome.
-
Contig
map
-
A map depicting the relative order of a linked library of
overlapping clones representing a complete chromosomal
segment.
-
Cosmid
-
Artificially constructed cloning vector containing the
cos gene of phage lambda. Cosmids can be packaged in
lambda phage particles for infection into E.
coli; this permits cloning of larger DNA fragments
(up to 45kb) than can be introduced into bacterial hosts
in plasmid vectors.
-
Crossing over
-
The breaking during meiosis of one maternal and one
paternal chromosome, the exchange of corresponding
sections of DNA, and the rejoining of the chromosomes.
This process can result in an exchange of alleles between
chromosomes.
See also:
recombination
-
Cytogenetics
-
The study of the physical appearance of
chromosomes.
See also: karyotype
-
Cytological band
-
An area of the chromosome that stains differently from
areas around it.
See also:
cytological map
-
Cytological map
-
A type of chromosome map whereby genes are located on the
basis of cytological findings obtained with the aid of
chromosome mutations.
-
Cytoplasmic (uniparental) inheritance
-
See: cytoplasmic trait
-
Cytoplasmic trait
-
A genetic characteristic in which the genes are found
outside the nucleus, in chloroplasts or mitochondria.
Results in offspring inheriting genetic material from
only one parent.
-
Cytosine (C)
-
A nitrogenous base, one member of the base pair GC
(guanine and cytosine) in DNA.
See also: base pair,
nucleotide
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-
Data warehouse
-
A collection of databases, data tables, and mechanisms to
access the data on a single subject.
-
Deletion
-
A loss of part of the DNA from a chromosome; can lead to
a disease or abnormality.
See also: chromosome,
mutation
-
Deletion map
-
A description of a specific chromosome that uses defined
mutations --specific deleted areas in the genome-- as
'biochemical signposts,' or markers for specific
areas.
-
Deoxyribonucleotide
-
See: nucleotide
-
Deoxyribose
-
A type of sugar that is one component of DNA
(deoxyribonucleic acid).
-
Diploid
-
A full set of genetic material consisting of paired
chromosomes, one from each parental set. Most animal
cells except the gametes have a diploid set of
chromosomes. The diploid human genome has 46
chromosomes.
See also: haploid
-
Directed evolution
-
A laboratory process used on isolated molecules or
microbes to cause mutations and identify subsequent
adaptations to novel environments.
-
Directed mutagenesis
-
Alteration of DNA at a specific site and its reinsertion
into an organism to study any effects of the change.
-
Directed sequencing
-
Successively sequencing DNA from adjacent stretches of
chromosome.
-
Disease-associated genes
-
Alleles carrying particular DNA sequences associated with
the presence of disease.
-
DNA
(deoxyribonucleic acid)
-
The molecule that encodes genetic information. DNA is a
double-stranded molecule held together by weak bonds
between base pairs of nucleotides. The four nucleotides
in DNA contain the bases adenine (A), guanine (G),
cytosine (C), and thymine (T). In nature, base pairs form
only between A and T and between G and C; thus the base
sequence of each single strand can be deduced from that
of its partner.
-
DNA
bank
-
A service that stores DNA extracted from blood samples or
other human tissue.
-
DNA
probe
-
See: probe
-
DNA repair genes
-
Genes encoding proteins that correct errors in DNA
sequencing.
-
DNA replication
-
The use of existing DNA as a template for the synthesis
of new DNA strands. In humans and other eukaryotes,
replication occurs in the cell nucleus.
-
DNA
sequence
-
The relative order of base pairs, whether in a DNA
fragment, gene, chromosome, or an entire genome.
See also:
base sequence analysis
-
Domain
-
A discrete portion of a protein with its own function.
The combination of domains in a single protein determines
its overall function.
-
Dominant
-
An allele that is almost always expressed, even if only
one copy is present.
See also: gene, genome
-
Double
helix
-
The twisted-ladder shape that two linear strands of DNA
assume when complementary nucleotides on opposing strands
bond together.
-
Draft sequence
-
The sequence generated by the HGP as of June 2000 that,
while incomplete, offers a virtual road map to an
estimated 95% of all human genes. Draft sequence data are
mostly in the form of 10,000 base pair-sized fragments
whose approximate chromosomal locations are known.
See also: sequencing,
finished DNA sequence,
working draft DNA sequence
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Electrophoresis
-
A method of separating large molecules (such as DNA
fragments or proteins) from a mixture of similar
molecules. An electric current is passed through a medium
containing the mixture, and each kind of molecule travels
through the medium at a different rate, depending on its
electrical charge and size. Agarose and acrylamide gels
are the media commonly used for electrophoresis of
proteins and nucleic acids.
-
Electroporation
-
A process using high-voltage current to make cell
membranes permeable to allow the introduction of new DNA;
commonly used in recombinant DNA technology.
See also: transfection
-
Embryonic stem
(ES) cells
-
An embryonic cell that can replicate indefinitely,
transform into other types of cells, and serve as a
continuous source of new cells.
-
Endonuclease
-
See: restriction enzyme
-
Enzyme
-
A protein that acts as a catalyst, speeding the rate at
which a biochemical reaction proceeds but not altering
the direction or nature of the reaction.
-
Epistasis
-
One gene interfers with or prevents the expression of
another gene located at a different locus.
-
Escherichia coli
-
Common bacterium that has been studied intensively by
geneticists because of its small genome size, normal lack
of pathogenicity, and ease of growth in the laboratory.
-
Eugenics
-
The study of improving a species by artificial selection;
usually refers to the selective breeding of humans.
-
Eukaryote
-
Cell or organism with membrane-bound, structurally
discrete nucleus and other well-developed subcellular
compartments. Eukaryotes include all organisms except
viruses, bacteria, and bluegreen algae.
See also: prokaryote,
chromosome.
-
Evolutionarily
conserved
-
See: conserved sequence
-
Exogenous DNA
-
DNA originating outside an organism that has been
introducted into the organism.
-
Exon
-
The protein-coding DNA sequence of a gene.
See also: intron
-
Exonuclease
-
An enzyme that cleaves nucleotides sequentially from free
ends of a linear nucleic acid substrate.
-
Expressed gene
-
See: gene expression
-
Expressed sequence
tag (EST)
-
A short strand of DNA that is a part of a cDNA molecule
and can act as identifier of a gene. Used in locating and
mapping genes.
See also: cDNA,
sequence tagged site
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Filial generation (F1, F2)
-
Each generation of offspring in a breeding program,
designated F1, F2, etc.
-
Fingerprinting
-
In genetics, the identification of multiple specific
alleles on a person's DNA to produce a unique
identifier for that person.
See also: forensics
-
Finished DNA Sequence
-
High-quality, low error, gap-free DNA sequence of the
human genome. Achieving this ultimate 2003 HGP goal
requires additional sequencing to close gaps, reduce
ambiguities, and allow for only a single error every
10,000 bases, the agreed-upon standard for HGP finished
sequence.
See also: sequencing,
draft sequence
-
Flow cytometry
-
Analysis of biological material by detection of the
light-absorbing or fluorescing properties of cells or
subcellular fractions (i.e., chromosomes) passing in a
narrow stream through a laser beam. An absorbance or
fluorescence profile of the sample is produced. Automated
sorting devices, used to fractionate samples, sort
successive droplets of the analyzed stream into different
fractions depending on the fluorescence emitted by each
droplet.
-
Flow karyotyping
-
Use of flow cytometry to analyze and separate chromosomes
according to their DNA content.
-
Fluorescence in situ hybridization (FISH)
-
A physical mapping approach that uses fluorescein tags to
detect hybridization of probes with metaphase chromosomes
and with the less-condensed somatic interphase chromatin.
-
Forensics
-
The use of DNA for identification. Some examples of DNA
use are to establish paternity in child support cases;
establish the presence of a suspect at a crime scene, and
identify accident victims.
-
Fraternal twin
-
Siblings born at the same time as the result of
fertilization of two ova by two sperm. They share the
same genetic relationship to each other as any other
siblings.
See also:
identical twin
-
Full gene sequence
-
The complete order of bases in a gene. This order
determines which protein a gene will produce.
-
Functional genomics
-
The study of genes, their resulting proteins, and the
role played by the proteins the body's biochemical
processes.
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Gamete
-
Mature male or female reproductive cell (sperm or ovum)
with a haploid set of chromosomes (23 for humans).
-
GC-rich
area
-
Many DNA sequences carry long stretches of repeated G and
C which often indicate a gene-rich region.
-
Gel electrophoresis
-
See: electrophoresis
-
Gene
-
The fundamental physical and functional unit of heredity.
A gene is an ordered sequence of nucleotides located in a
particular position on a particular chromosome that
encodes a specific functional product (i.e., a protein or
RNA molecule).
See also:
gene expression
-
Gene amplification
-
Repeated copying of a piece of DNA; a characteristic of
tumor cells.
See also: gene,
oncogene
-
Gene chip technology
-
Development of cDNA microarrays from a large number of
genes. Used to monitor and measure changes in gene
expression for each gene represented on the chip.
-
Gene expression
-
The process by which a gene's coded information is
converted into the structures present and operating in
the cell. Expressed genes include those that are
transcribed into mRNA and then translated into protein
and those that are transcribed into RNA but not
translated into protein (e.g., transfer and ribosomal
RNAs).
-
Gene
family
-
Group of closely related genes that make similar
products.
-
Gene
library
-
See: genomic library
-
Gene
mapping
-
Determination of the relative positions of genes on a DNA
molecule (chromosome or plasmid) and of the distance, in
linkage units or physical units, between them.
-
Gene
pool
-
All the variations of genes in a species.
See also: allele, gene,
polymorphism
-
Gene prediction
-
Predictions of possible genes made by a computer program
based on how well a stretch of DNA sequence matches known
gene sequences
-
Gene
product
-
The biochemical material, either RNA or protein,
resulting from expression of a gene. The amount of gene
product is used to measure how active a gene is; abnormal
amounts can be correlated with disease-causing alleles.
-
Gene
testing
-
See: genetic testing,
genetic screening
-
Gene
therapy
-
An experimental procedure aimed at replacing,
manipulating, or supplementing nonfunctional or
misfunctioning genes with healthy genes.
See also: gene, inherit,
somatic cell gene therapy,
germ line gene therapy
-
Gene
transfer
-
Incorporation of new DNA into and organism's cells,
usually by a vector such as a modified virus. Used in
gene therapy.
See also: mutation,
gene
therapy, vector
-
Genetic
code
-
The sequence of nucleotides, coded in triplets (codons)
along the mRNA, that determines the sequence of amino
acids in protein synthesis. A gene's DNA sequence can
be used to predict the mRNA sequence, and the genetic
code can in turn be used to predict the amino acid
sequence.
-
Genetic counseling
-
Provides patients and their families with education and
information about genetic-related conditions and helps
them make informed decisions.
-
Genetic
discrimination
-
Prejudice against those who have or are likely to develop
an inherited disorder.
-
Genetic engineering
-
Altering the genetic material of cells or organisms to
enable them to make new substances or perform new
functions.
-
Genetic
engineering technology
-
See:
recombinant DNA technology
-
Genetic illness
-
Sickness, physical disability, or other disorder
resulting from the inheritance of one or more deleterious
alleles.
-
Genetic informatics
-
See: bioinformatics
-
Genetic
map
-
See: linkage map
-
Genetic marker
-
A gene or other identifiable portion of DNA whose
inheritance can be followed.
See also: chromosome,
DNA,
gene,
inherit
-
Genetic material
-
See: genome
-
Genetic mosaic
-
An organism in which different cells contain different
genetic sequence. This can be the result of a mutation
during development or fusion of embryos at an early
developmental stage.
-
Genetic polymorphism
-
Difference in DNA sequence among individuals, groups, or
populations (e.g., genes for blue eyes versus brown
eyes).
-
Genetic
predisposition
-
Susceptibility to a genetic disease. May or may not
result in actual development of the disease.
-
Genetic screening
-
Testing a group of people to identify individuals at high
risk of having or passing on a specific genetic disorder.
-
Genetic testing
-
Analyzing an individual's genetic material to
determine predisposition to a particular health condition
or to confirm a diagnosis of genetic disease.
-
Genetics
-
The study of inheritance patterns of specific traits.
-
Genome
-
All the genetic material in the chromosomes of a
particular organism; its size is generally given as its
total number of base pairs.
-
Genome project
-
Research and technology-development effort aimed at
mapping and sequencing the genome of human beings and
certain model organisms.
See also:
Human Genome Initiative
-
Genomic library
-
A collection of clones made from a set of randomly
generated overlapping DNA fragments that represent the
entire genome of an organism.
See also: library,
arrayed library
-
Genomic sequence
-
See: DNA
-
Genomics
-
The study of genes and their function.
-
Genotype
-
The genetic constitution of an organism, as distinguished
from its physical appearance (its phenotype).
-
Germ
cell
-
Sperm and egg cells and their precursors. Germ cells are
haploid and have only one set of chromosomes (23 in all),
while all other cells have two copies (46 in all).
-
Germ
line
-
The continuation of a set of genetic information from one
generation to the next.
See also: inherit
-
Germ line gene therapy
-
An experimental process of inserting genes into germ
cells or fertilized eggs to cause a genetic change that
can be passed on to offspring. May be used to alleviate
effects associated with a genetic disease.
See also: genomics,
somatic cell gene therapy.
-
Germ line genetic
mutation
-
See: mutation
-
Guanine (G)
-
A nitrogenous base, one member of the base pair GC
(guanine and cytosine) in DNA.
See also: base pair,
nucleotide
-
Gyandromorph
-
Organisms that have both male and female cells and
therefore express both male and female characteristics.
Return to Top
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Haploid
-
A single set of chromosomes (half the full set of genetic
material) present in the egg and sperm cells of animals
and in the egg and pollen cells of plants. Human beings
have 23 chromosomes in their reproductive cells.
See also: diploid
-
Haplotype
-
A way of denoting the collective genotype of a number of
closely linked loci on a chromosome.
-
Hemizygous
-
Having only one copy of a particular gene. For example,
in humans, males are hemizygous for genes found on the Y
chromosome.
-
Hereditary cancer
-
Cancer that occurs due to the inheritance of an altered
gene within a family.
See also:
sporadic cancer
-
Heterozygosity
-
The presence of different alleles at one or more loci on
homologous chromosomes.
-
Heterozygote
-
See: heterozygosity
-
Highly conserved
sequence
-
DNA sequence that is very similar across several
different types of organisms.
See also: gene,
mutation
-
High-throughput
sequencing
-
A fast method of determining the order of bases in
DNA.
See also: sequencing
-
Homeobox
-
A short stretch of nucleotides whose base sequence is
virtually identical in all the genes that contain it.
Homeoboxes have been found in many organisms from fruit
flies to human beings. In the fruit fly, a homeobox
appears to determine when particular groups of genes are
expressed during development.
-
Homolog
-
A member of a chromosome pair in diploid organisms or a
gene that has the same origin and functions in two or
more species.
-
Homologous
chromosome
-
Chromosome containing the same linear gene sequences as
another, each derived from one parent.
-
Homologous
recombination
-
Swapping of DNA fragments between paired chromosomes.
-
Homology
-
Similarity in DNA or protein sequences between
individuals of the same species or among different
species.
-
Homozygote
-
An organism that has two identical alleles of a
gene.
See also: heterozygote
-
Homozygous
-
See: homozygote
-
Human
artificial chromosome (HAC)
-
A vector used to hold large DNA fragments.
See also: chromosome,
DNA
-
Human gene therapy
-
See: gene therapy
-
Human Genome
Initiative
-
Collective name for several projects begun in 1986 by DOE
to create an ordered set of DNA segments from known
chromosomal locations, develop new computational methods
for analyzing genetic map and DNA sequence data, and
develop new techniques and instruments for detecting and
analyzing DNA. This DOE initiative is now known as the
Human Genome Program. The joint national effort, led by
DOE and NIH, is known as the Human Genome Project.
-
Human Genome Project (HGP)
-
Formerly titled Human Genome Initiative.
See also:
Human Genome Initiative
-
Hybrid
-
The offspring of genetically different parents.
See also: heterozygote
-
Hybridization
-
The process of joining two complementary strands of DNA
or one each of DNA and RNA to form a double-stranded
molecule.
Return to Top
-
Identical twin
-
Twins produced by the division of a single zygote; both
have identical genotypes.
See also:
fraternal twin
-
Immunotherapy
-
Using the immune system to treat disease, for example, in
the development of vaccines. May also refer to the
therapy of diseases caused by the immune system.
See also: cancer
-
Imprinting
-
A phenomenon in which the disease phenotype depends on
which parent passed on the disease gene. For instance,
both Prader-Willi and Angelman syndromes are inherited
when the same part of chromosome 15 is missing. When the
father's complement of 15 is missing, the child has
Prader-Willi, but when the mother's complement of 15
is missing, the child has Angelman syndrome.
-
In situ hybridization
-
Use of a DNA or RNA probe to detect the presence of the
complementary DNA sequence in cloned bacterial or
cultured eukaryotic cells.
-
In
vitro
-
Studies performed outside a living organism such as in a
laboratory.
-
In vivo
-
Studies carried out in living organisms.
-
Independent
assortment
-
During meiosis each of the two copies of a gene is
distributed to the germ cells independently of the
distribution of other genes.
See also: linkage
-
Informatics
-
See: bioinformatics
-
Informed consent
-
An individual willingly agrees to participate in an
activity after first being advised of the risks and
benefits.
See also: privacy
-
Inherit
-
In genetics, to receive genetic material from parents
through biological processes.
-
Inherited
-
See: inherit
-
Insertion
-
A chromosome abnormality in which a piece of DNA is
incorporated into a gene and thereby disrupts the
gene's normal function.
See also: chromosome,
DNA,
gene,
mutation
-
Insertional mutation
-
See: insertion
-
Intellectual
property rights
-
Patents, copyrights, and trademarks.
See also: patent
-
Interference
-
One crossover event inhibits the chances of another
crossover event. Also known as positive interference.
Negative interference increases the chance of a second
crossover.
See also: crossing over
-
Interphase
-
The period in the cell cycle when DNA is replicated in
the nucleus; followed by mitosis.
-
Intron
-
DNA sequence that interrupts the protein-coding sequence
of a gene; an intron is transcribed into RNA but is cut
out of the message before it is translated into
protein.
See also: exon
-
Isoenzyme
-
An enzyme performing the same function as another enzyme
but having a different set of amino acids. The two
enzymes may function at different speeds.
Return to Top
-
Junk
DNA
-
Stretches of DNA that do not code for genes; most of the
genome consists of so-called junk DNA which may have
regulatory and other functions. Also called non-coding
DNA.
Return to Top
-
Karyotype
-
A photomicrograph of an individual's chromosomes
arranged in a standard format showing the number, size,
and shape of each chromosome type; used in low-resolution
physical mapping to correlate gross chromosomal
abnormalities with the characteristics of specific
diseases.
-
Kilobase (kb)
-
Unit of length for DNA fragments equal to 1000
nucleotides.
-
Knockout
-
Deactivation of specific genes; used in laboratory
organisms to study gene function.
See also: gene, locus,
model organisms
Return to Top
-
Library
-
An unordered collection of clones (i.e., cloned DNA from
a particular organism) whose relationship to each other
can be established by physical mapping.
See also:
genomic library,
arrayed library
-
Linkage
-
The proximity of two or more markers (e.g., genes, RFLP
markers) on a chromosome; the closer the markers, the
lower the probability that they will be separated during
DNA repair or replication processes (binary fission in
prokaryotes, mitosis or meiosis in eukaryotes), and hence
the greater the probability that they will be inherited
together.
-
Linkage
disequilibrium
-
Where alleles occur together more often than can be
accounted for by chance. Indicates that the two alleles
are physically close on the DNA strand.
See also:
Mendelian inheritance
-
Linkage
map
-
A map of the relative positions of genetic loci on a
chromosome, determined on the basis of how often the loci
are inherited together. Distance is measured in
centimorgans (cM).
-
Localize
-
Determination of the original position (locus) of a gene
or other marker on a chromosome.
-
Locus (pl. loci)
-
The position on a chromosome of a gene or other
chromosome marker; also, the DNA at that position. The
use of locus is sometimes restricted to mean expressed
DNA regions.
See also:
gene expression
-
Long-Range
Restriction Mapping
-
Restriction enzymes are proteins that cut DNA at precise
locations. Restriction maps depict the chromosomal
positions of restriction-enzyme cutting sites. These are
used as biochemical "signposts," or markers of
specific areas along the chromosomes. The map will detail
the positions where the DNA molecule is cut by particular
restriction enzymes.
Return to Top
-
Macrorestriction map
-
Map depicting the order of and distance between sites at
which restriction enzymes cleave chromosomes.
-
Mapping
-
See: gene mapping,
linkage map,
physical map
-
Mapping population
-
The group of related organisms used in constructing a
genetic map.
-
Marker
-
See: genetic marker
-
Mass spectrometry
-
An instrument used to identify chemicals in a substance
by their mass and charge.
-
Megabase (Mb)
-
Unit of length for DNA fragments equal to 1 million
nucleotides and roughly equal to 1 cM.
See also: centimorgan
-
Meiosis
-
The process of two consecutive cell divisions in the
diploid progenitors of sex cells. Meiosis results in four
rather than two daughter cells, each with a haploid set
of chromosomes.
See also: mitosis
-
Mendelian
inheritance
-
One method in which genetic traits are passed from
parents to offspring. Named for Gregor Mendel, who first
studied and recognized the existence of genes and this
method of inheritance.
See also:
autosomal dominant,
recessive gene,
sex-linked
-
Messenger RNA (mRNA)
-
RNA that serves as a template for protein
synthesis.
See also: genetic code
-
Metaphase
-
A stage in mitosis or meiosis during which the
chromosomes are aligned along the equatorial plane of the
cell.
-
Microarray
-
Sets of miniaturized chemical reaction areas that may
also be used to test DNA fragments, antibodies, or
proteins.
-
Microbial genetics
-
The study of genes and gene function in bacteria,
archaea, and other microorganisms. Often used in research
in the fields of bioremediation, alternative energy, and
disease prevention.
See also:
model organisms,
biotechnology,
bioremediation
-
Microinjection
-
A technique for introducing a solution of DNA into a cell
using a fine microcapillary pipet.
-
Micronuclei
-
Chromosome fragments that are not incorporated into the
nucleus at cell division.
-
Mitochondrial DNA
-
The genetic material found in mitochondria, the
organelles that generate energy for the cell. Not
inherited in the same fashion as nucleic DNA.
See also: cell, DNA, genome,
nucleus
-
Mitosis
-
The process of nuclear division in cells that produces
daughter cells that are genetically identical to each
other and to the parent cell.
See also: meiosis
-
Model organisms
-
A laboratory animal or other organism useful for
research.
-
Modeling
-
The use of statistical analysis, computer analysis, or
model organisms to predict outcomes of research.
-
Molecular biology
-
The study of the structure, function, and makeup of
biologically important molecules.
-
Molecular farming
-
The development of transgenic animals to produce human
proteins for medical use.
-
Molecular genetics
-
The study of macromolecules important in biological
inheritance.
-
Molecular medicine
-
The treatment of injury or disease at the molecular
level. Examples include the use of DNA-based diagnostic
tests or medicine derived from DNA sequence information.
-
Monogenic disorder
-
A disorder caused by mutation of a single gene.
See also: mutation,
polygenic disorder
-
Monogenic
inheritance
-
See: monogenic disorder
-
Monosomy
-
Possessing only one copy of a particular chromosome
instead of the normal two copies.
See also: cell,
chromosome,
gene expression,
trisomy
-
Morbid
map
-
A diagram showing the chromosomal location of genes
associated with disease.
-
Mouse
model
-
See: model organisms
-
Multifactorial or multigenic disorder
-
See: polygenic disorder
-
Multiplexing
-
A laboratory approach that performs multiple sets of
reactions in parallel (simultaneously); greatly
increasing speed and throughput.
-
Murine
-
Organism in the genus Mus. A rat or mouse.
-
Mutagen
-
An agent that causes a permanent genetic change in a
cell. Does not include changes occurring during normal
genetic recombination.
-
Mutagenicity
-
The capacity of a chemical or physical agent to cause
permanent genetic alterations.
See also:
somatic cell genetic mutation
-
Mutation
-
Any heritable change in DNA sequence.
See also: polymorphism
Return to Top
-
Nitrogenous base
-
A nitrogen-containing molecule having the chemical
properties of a base. DNA contains the nitrogenous bases
adenine (A), guanine (G), cytosine (C), and thymine
(T).
See also: DNA
-
Northern blot
-
A gel-based laboratory procedure that locates mRNA
sequences on a gel that are complementary to a piece of
DNA used as a probe.
See also: DNA, library
-
Nuclear transfer
-
A laboratory procedure in which a cell's nucleus is
removed and placed into an oocyte with its own nucleus
removed so the genetic information from the donor nucleus
controls the resulting cell. Such cells can be induced to
form embryos. This process was used to create the cloned
sheep "Dolly".
See also: cloning
-
Nucleic
acid
-
A large molecule composed of nucleotide subunits.
See also: DNA
-
Nucleolar
organizing region
-
A part of the chromosome containing rRNA genes.
-
Nucleotide
-
A subunit of DNA or RNA consisting of a nitrogenous base
(adenine, guanine, thymine, or cytosine in DNA; adenine,
guanine, uracil, or cytosine in RNA), a phosphate
molecule, and a sugar molecule (deoxyribose in DNA and
ribose in RNA). Thousands of nucleotides are linked to
form a DNA or RNA molecule.
See also: DNA, base pair,
RNA
-
Nucleus
-
The cellular organelle in eukaryotes that contains most
of the genetic material.
Return to Top
-
Oligo
-
See: oligonucleotide
-
Oligogenic
-
A phenotypic trait produced by two or more genes working
together.
See also:
polygenic disorder
-
Oligonucleotide
-
A molecule usually composed of 25 or fewer nucleotides;
used as a DNA synthesis primer.
See also: nucleotide
-
Oncogene
-
A gene, one or more forms of which is associated with
cancer. Many oncogenes are involved, directly or
indirectly, in controlling the rate of cell growth.
-
Open reading frame (ORF)
-
The sequence of DNA or RNA located between the start-code
sequence (initiation codon) and the stop-code sequence
(termination codon).
-
Operon
-
A set of genes transcribed under the control of an
operator gene.
-
Overlapping clones
-
See: genomic library
Return to Top
-
P1-derived
artificial chromosome (PAC)
-
One type of vector used to clone DNA fragments (100- to
300-kb insert size; average, 150 kb) in Escherichia
coli cells. Based on bacteriophage (a virus) P1
genome.
See also:
cloning vector
-
Patent
-
In genetics, conferring the right or title to genes, gene
variations, or identifiable portions of sequenced genetic
material to an individual or organization.
See also: gene
-
Pedigree
-
A family tree diagram that shows how a particular genetic
trait or disease has been inherited.
See also: inherit
-
Penetrance
-
The probability of a gene or genetic trait being
expressed. "Complete" penetrance means the gene
or genes for a trait are expressed in all the population
who have the genes. "Incomplete" penetrance
means the genetic trait is expressed in only part of the
population. The percent penetrance also may change with
the age range of the population.
-
Peptide
-
Two or more amino acids joined by a bond called a
"peptide bond."
See also: polypeptide
-
Phage
-
A virus for which the natural host is a bacterial cell.
-
Pharmacogenomics
-
The study of the interaction of an individual's
genetic makeup and response to a drug.
-
Phenocopy
-
A trait not caused by inheritance of a gene but appears
to be identical to a genetic trait.
-
Phenotype
-
The physical characteristics of an organism or the
presence of a disease that may or may not be
genetic.
See also: genotype
-
Physical map
-
A map of the locations of identifiable landmarks on DNA
(e.g., restriction-enzyme cutting sites, genes),
regardless of inheritance. Distance is measured in base
pairs. For the human genome, the lowest-resolution
physical map is the banding patterns on the 24 different
chromosomes; the highest-resolution map is the complete
nucleotide sequence of the chromosomes.
-
Plasmid
-
Autonomously replicating extra-chromosomal circular DNA
molecules, distinct from the normal bacterial genome and
nonessential for cell survival under nonselective
conditions. Some plasmids are capable of integrating into
the host genome. A number of artificially constructed
plasmids are used as cloning vectors.
-
Pleiotropy
-
One gene that causes many different physical traits such
as multiple disease symptoms.
-
Pluripotency
-
The potential of a cell to develop into more than one
type of mature cell, depending on environment.
-
Polygenic disorder
-
Genetic disorder resulting from the combined action of
alleles of more than one gene (e.g., heart disease,
diabetes, and some cancers). Although such disorders are
inherited, they depend on the simultaneous presence of
several alleles; thus the hereditary patterns usually are
more complex than those of single-gene disorders.
See also:
single-gene disorder
-
Polymerase chain
reaction (PCR)
-
A method for amplifying a DNA base sequence using a
heat-stable polymerase and two 20-base primers, one
complementary to the (+) strand at one end of the
sequence to be amplified and one complementary to the (-)
strand at the other end. Because the newly synthesized
DNA strands can subsequently serve as additional
templates for the same primer sequences, successive
rounds of primer annealing, strand elongation, and
dissociation produce rapid and highly specific
amplification of the desired sequence. PCR also can be
used to detect the existence of the defined sequence in a
DNA sample.
-
Polymerase, DNA or RNA
-
Enzyme that catalyzes the synthesis of nucleic acids on
preexisting nucleic acid templates, assembling RNA from
ribonucleotides or DNA from deoxyribonucleotides.
-
Polymorphism
-
Difference in DNA sequence among individuals that may
underlie differences in health. Genetic variations
occurring in more than 1% of a population would be
considered useful polymorphisms for genetic linkage
analysis.
See also: mutation
-
Polypeptide
-
A protein or part of a protein made of a chain of amino
acids joined by a peptide bond.
-
Population genetics
-
The study of variation in genes among a group of
individuals.
-
Positional cloning
-
A technique used to identify genes, usually those that
are associated with diseases, based on their location on
a chromosome.
-
Premature
chromosome condensation (PCC)
-
A method of studying chromosomes in the interphase stage
of the cell cycle.
-
Primer
-
Short preexisting polynucleotide chain to which new
deoxyribonucleotides can be added by DNA polymerase.
-
Privacy
-
In genetics, the right of people to restrict access to
their genetic information.
-
Probe
-
Single-stranded DNA or RNA molecules of specific base
sequence, labeled either radioactively or
immunologically, that are used to detect the
complementary base sequence by hybridization.
-
Prokaryote
-
Cell or organism lacking a membrane-bound, structurally
discrete nucleus and other subcellular compartments.
Bacteria are examples of prokaryotes.
See also: chromosome,
eukaryote
-
Promoter
-
A DNA site to which RNA polymerase will bind and initiate
transcription.
-
Pronucleus
-
The nucleus of a sperm or egg prior to
fertilization.
See also: nucleus,
transgenic
-
Protein
-
A large molecule composed of one or more chains of amino
acids in a specific order; the order is determined by the
base sequence of nucleotides in the gene that codes for
the protein. Proteins are required for the structure,
function, and regulation of the body's cells,
tissues, and organs; and each protein has unique
functions. Examples are hormones, enzymes, and
antibodies.
-
Proteome
-
Proteins expressed by a cell or organ at a particular
time and under specific conditions.
-
Proteomics
-
The study of the full set of proteins encoded by a
genome.
-
Pseudogene
-
A sequence of DNA similar to a gene but nonfunctional;
probably the remnant of a once-functional gene that
accumulated mutations.
-
Purine
-
A nitrogen-containing, double-ring, basic compound that
occurs in nucleic acids. The purines in DNA and RNA are
adenine and guanine.
See also: base pair
-
Pyrimidine
-
A nitrogen-containing, single-ring, basic compound that
occurs in nucleic acids. The pyrimidines in DNA are
cytosine and thymine; in RNA, cytosine and uracil.
See also: base pair
Return to Top
-
Radiation hybrid
-
A hybrid cell containing small fragments of irradiated
human chromosomes. Maps of irradiation sites on
chromosomes for the human, rat, mouse, and other genomes
provide important markers, allowing the construction of
very precise STS maps indispensable to studying
multifactorial diseases.
See also:
sequence tagged site
-
Rare-cutter enzyme
-
See:
restriction-enzyme cutting site
-
Recessive gene
-
A gene which will be expressed only if there are 2
identical copies or, for a male, if one copy is present
on the X chromosome.
-
Reciprocal
translocation
-
When a pair of chromosomes exchange exactly the same
length and area of DNA. Results in a shuffling of genes.
-
Recombinant clone
-
Clone containing recombinant DNA molecules.
See also:
recombinant DNA technology
-
Recombinant DNA
molecules
-
A combination of DNA molecules of different origin that
are joined using recombinant DNA technologies.
-
Recombinant DNA
technology
-
Procedure used to join together DNA segments in a
cell-free system (an environment outside a cell or
organism). Under appropriate conditions, a recombinant
DNA molecule can enter a cell and replicate there, either
autonomously or after it has become integrated into a
cellular chromosome.
-
Recombination
-
The process by which progeny derive a combination of
genes different from that of either parent. In higher
organisms, this can occur by crossing over.
See also: crossing over,
mutation
-
Regulatory
region or sequence
-
A DNA base sequence that controls gene expression.
-
Repetitive DNA
-
Sequences of varying lengths that occur in multiple
copies in the genome; it represents much of the human
genome.
-
Reporter gene
-
See: marker
-
Resolution
-
Degree of molecular detail on a physical map of DNA,
ranging from low to high.
-
Restriction enzyme, endonuclease
-
A protein that recognizes specific, short nucleotide
sequences and cuts DNA at those sites. Bacteria contain
over 400 such enzymes that recognize and cut more than
100 different DNA sequences.
See also:
restriction enzyme cutting site
-
Restriction fragment length polymorphism
(RFLP)
-
Variation between individuals in DNA fragment sizes cut
by specific restriction enzymes; polymorphic sequences
that result in RFLPs are used as markers on both physical
maps and genetic linkage maps. RFLPs usually are caused
by mutation at a cutting site.
See also: marker,
polymorphism
-
Restriction-enzyme cutting site
-
A specific nucleotide sequence of DNA at which a
particular restriction enzyme cuts the DNA. Some sites
occur frequently in DNA (e.g., every several hundred base
pairs); others much less frequently (rare-cutter; e.g.,
every 10,000 base pairs).
-
Retroviral infection
-
The presence of retroviral vectors, such as some viruses,
which use their recombinant DNA to insert their genetic
material into the chromosomes of the host's cells.
The virus is then propogated by the host cell.
-
Reverse
transcriptase
-
An enzyme used by retroviruses to form a complementary
DNA sequence (cDNA) from their RNA. The resulting DNA is
then inserted into the chromosome of the host cell.
-
Ribonucleotide
-
See: nucleotide
-
Ribose
-
The five-carbon sugar that serves as a component of
RNA.
See also:
ribonucleic acid,
deoxyribose
-
Ribosomal RNA (rRNA)
-
A class of RNA found in the ribosomes of cells.
-
Ribosomes
-
Small cellular components composed of specialized
ribosomal RNA and protein; site of protein
synthesis.
See also: RNA
-
Risk communication
-
In genetics, a process in which a genetic counselor or
other medical professional interprets genetic test
results and advises patients of the consequences for them
and their offspring.
-
RNA
(Ribonucleic acid)
-
A chemical found in the nucleus and cytoplasm of cells;
it plays an important role in protein synthesis and other
chemical activities of the cell. The structure of RNA is
similar to that of DNA. There are several classes of RNA
molecules, including messenger RNA, transfer RNA,
ribosomal RNA, and other small RNAs, each serving a
different purpose.
Return to Top
-
Sanger sequencing
-
A widely used method of determining the order of bases in
DNA.
See also: sequencing,
shotgun sequencing
-
Satellite
-
A chromosomal segment that branches off from the rest of
the chromosome but is still connected by a thin filament
or stalk.
-
Scaffold
-
In genomic mapping, a series of contigs that are in the
right order but not necessarily connected in one
continuous stretch of sequence.
-
Segregation
-
The normal biological process whereby the two pieces of a
chromosome pair are separated during meiosis and randomly
distributed to the germ cells.
-
Sequence
-
See: base sequence
-
Sequence assembly
-
A process whereby the order of multiple sequenced DNA
fragments is determined.
-
Sequence tagged site (STS)
-
Short (200 to 500 base pairs) DNA sequence that has a
single occurrence in the human genome and whose location
and base sequence are known. Detectable by polymerase
chain reaction, STSs are useful for localizing and
orienting the mapping and sequence data reported from
many different laboratories and serve as landmarks on the
developing physical map of the human genome. Expressed
sequence tags (ESTs) are STSs derived from cDNAs.
-
Sequencing
-
Determination of the order of nucleotides (base
sequences) in a DNA or RNA molecule or the order of amino
acids in a protein.
-
Sequencing
technology
-
The instrumentation and procedures used to determine the
order of nucleotides in DNA.
-
Sex
chromosome
-
The X or Y chromosome in human beings that determines the
sex of an individual. Females have two X chromosomes in
diploid cells; males have an X and a Y chromosome. The
sex chromosomes comprise the 23rd chromosome pair in a
karyotype.
See also: autosome
-
Sex-linked
-
Traits or diseases associated with the X or Y chromosome;
generally seen in males.
See also: gene,
mutation,
sex
chromosome
-
Shotgun method
-
Sequencing method that involves randomly sequenced cloned
pieces of the genome, with no foreknowledge of where the
piece originally came from. This can be contrasted with
"directed" strategies, in which pieces of DNA
from known chromosomal locations are sequenced. Because
there are advantages to both strategies, researchers use
both random (or shotgun) and directed strategies in
combination to sequence the human genome.
See also: library,
genomic library
-
Single
nucleotide polymorphism (SNP)
-
DNA sequence variations that occur when a single
nucleotide (A, T, C, or G) in the genome sequence is
altered.
See also: mutation,
polymorphism,
single-gene disorder
-
Single-gene disorder
-
Hereditary disorder caused by a mutant allele of a single
gene (e.g., Duchenne muscular dystrophy, retinoblastoma,
sickle cell disease).
See also:
polygenic disorders
-
Somatic
cell
-
Any cell in the body except gametes and their
precursors.
See also: gamete
-
Somatic cell gene
therapy
-
Incorporating new genetic material into cells for
therapeutic purposes. The new genetic material cannot be
passed to offspring.
See also: gene therapy
-
Somatic cell
genetic mutation
-
A change in the genetic structure that is neither
inherited nor passed to offspring. Also called acquired
mutations.
See also:
germ line genetic mutation
-
Southern blotting
-
Transfer by absorption of DNA fragments separated in
electrophoretic gels to membrane filters for detection of
specific base sequences by radio-labeled complementary
probes.
-
Spectral karyotype (SKY)
-
A graphic of all an organism's chromosomes, each
labeled with a different color. Useful for identifying
chromosomal abnormalities.
See also: chromosome
-
Splice
site
-
Location in the DNA sequence where RNA removes the
noncoding areas to form a continuous gene transcript for
translation into a protein.
-
Sporadic cancer
-
Cancer that occurs randomly and is not inherited from
parents. Caused by DNA changes in one cell that grows and
divides, spreading throughout the body.
See also:
hereditary cancer
-
Stem
cell
-
Undifferentiated, primitive cells in the bone marrow that
have the ability both to multiply and to differentiate
into specific blood cells.
-
Structural genomics
-
The effort to determine the 3D structures of large
numbers of proteins using both experimental techniques
and computer simulation
-
Substitution
-
In genetics, a type of mutation due to replacement of one
nucleotide in a DNA sequence by another nucleotide or
replacement of one amino acid in a protein by another
amino acid.
See also: mutation
-
Suppressor gene
-
A gene that can suppress the action of another gene.
-
Syndrome
-
The group or recognizable pattern of symptoms or
abnormalities that indicate a particular trait or
disease.
-
Syngeneic
-
Genetically identical members of the same species.
-
Synteny
-
Genes occurring in the same order on chromosomes of
different species.
See also: linkage,
conserved sequence
Return to Top
-
Tandem repeat
sequences
-
Multiple copies of the same base sequence on a
chromosome; used as markers in physical mapping.
See also: physical map
-
Targeted mutagenesis
-
Deliberate change in the genetic structure directed at a
specific site on the chromosome. Used in research to
determine the targeted region's function.
See also: mutation,
polymorphism
-
Technology transfer
-
The process of transferring scientific findings from
research laboratories to the commercial sector.
-
Telomerase
-
The enzyme that directs the replication of telomeres.
-
Telomere
-
The end of a chromosome. This specialized structure is
involved in the replication and stability of linear DNA
molecules.
See also:
DNA replication
-
Teratogenic
-
Substances such as chemicals or radiation that cause
abnormal development of a embryo.
See also: mutatgen
-
Thymine (T)
-
A nitrogenous base, one member of the base pair AT
(adenine-thymine).
See also: base pair,
nucleotide
-
Toxicogenomics
-
The study of how genomes respond to environmental
stressors or toxicants. Combines genome-wide mRNA
expression profiling with protein expression patterns
using bioinformatics to understand the role of
gene-environment interactions in disease and dysfunction.
-
Transcription
-
The synthesis of an RNA copy from a sequence of DNA (a
gene); the first step in gene expression.
See also: translation
-
Transcription factor
-
A protein that binds to regulatory regions and helps
control gene expression.
-
Transcriptome
-
The full complement of activated genes, mRNAs, or
transcripts in a particular tissue at a particular time
-
Transfection
-
The introduction of foreign DNA into a host cell.
See also:
cloning vector,
gene
therapy
-
Transfer RNA (tRNA)
-
A class of RNA having structures with triplet nucleotide
sequences that are complementary to the triplet
nucleotide coding sequences of mRNA. The role of tRNAs in
protein synthesis is to bond with amino acids and
transfer them to the ribosomes, where proteins are
assembled according to the genetic code carried by mRNA.
-
Transformation
-
A process by which the genetic material carried by an
individual cell is altered by incorporation of exogenous
DNA into its genome.
-
Transgenic
-
An experimentally produced organism in which DNA has been
artificially introduced and incorporated into the
organism's germ line.
See also: cell, DNA, gene, nucleus,
germ
line
-
Translation
-
The process in which the genetic code carried by mRNA
directs the synthesis of proteins from amino acids.
See also:
transcription
-
Translocation
-
A mutation in which a large segment of one chromosome
breaks off and attaches to another chromosome.
See also: mutation
-
Transposable element
-
A class of DNA sequences that can move from one
chromosomal site to another.
-
Trisomy
-
Possessing three copies of a particular chromosome
instead of the normal two copies.
See also: cell, gene,
gene expression,
chromosome
Return to Top
-
Uracil
-
A nitrogenous base normally found in RNA but not DNA;
uracil is capable of forming a base pair with
adenine.
See also: base pair,
nucleotide
Return to Top
-
Vector
-
See: cloning vector
-
Virus
-
A noncellular biological entity that can reproduce only
within a host cell. Viruses consist of nucleic acid
covered by protein; some animal viruses are also
surrounded by membrane. Inside the infected cell, the
virus uses the synthetic capability of the host to
produce progeny virus.
See also:
cloning vector
Return to Top
-
Western
blot
-
A technique used to identify and locate proteins based on
their ability to bind to specific antibodies.
See also: DNA,
Northern blot,
protein, RNA,
Southern blotting
-
Wild
type
-
The form of an organism that occurs most frequently in
nature.
-
Working Draft DNA
Sequence
-
See: Draft DNA Sequence
Return to Top
-
X
chromosome
-
One of the two sex chromosomes, X and Y.
See also: Y chromosome,
sex
chromosome
-
Xenograft
-
Tissue or organs from an individual of one species
transplanted into or grafted onto an organism of another
species, genus, or family. A common example is the use of
pig heart valves in humans.
Return to Top
-
Y
chromosome
-
One of the two sex chromosomes, X and Y.
See also: X chromosome,
sex
chromosome
-
Yeast
artificial chromosome (YAC)
-
Constructed from yeast DNA, it is a vector used to clone
large DNA fragments.
See also:
cloning vector,
cosmid
Return to Top
-
Zinc-finger protein
-
A secondary feature of some proteins containing a zinc
atom; a DNA-binding protein.
Return to Top
Updated 12-May-05
Now Featuring
FUNDING CALL: Genomic Science: Biosystems Design to Enable Next-Generation Biofuels
Biosystems Design: DRAFT Report from the July 2011 Workshop
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Application Due: February 24, 2012
- 2012 Genomic Science Meeting will be held February 26-29, 2012 , at the Bethesda North Marriott Hotel and Conference Center. Abstract deadline December 15, 2011. Attendance by invitation only.
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- DOE and USDA Fund Ten New Projects for Biomass Genomics Research. See press release.
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