Key
words and concepts in DNA-assisted breeding programs
AFLPs (Amplified fragment length polymorphisms): A
type of molecular marker sometimes used to identify differences among populations and
sub-populations of an animal.
Alleles: Alternative forms of various genetic units; the term is
traditionally associated with different forms of a gene, but is now used in reference to
different forms of any kind of identifiable genetic element.
Allozymes: A category of proteins often used as genetic markers
because different alleles can often be readily by electrophoresis.
Chromosome: Structures in a cell nucleus that contain most of the
genetic material of the cell, including nearly all of the genes.
Cloning: Production of genetically identical cells from a single
starting cell.
Dendogram: A computer-generated figure that shows the genetic
relationships among the members of a population of animals
DNA bases: The fundamental units that make up DNA. There are four
kinds of bases, designated A, T, G and C. The genetic information that defines an animal
is encoded in the sequence of bases present in its DNA.
DNA sequence: The specific sequence of bases (A’s, T’s,
G’s and C’s) present in a molecule, or a portion of a molecule, of DNA.
Electrophoresis: A method of separating electrically charged
molecules (e.g., ions of DNA or protein)) in an electric field by passage through an
agarose or acrylamide gel (or other) that separates on the basis of electric charge and
mass of the molecule.
Enrichment: A process that increases the proportion of desirable
molecules in a mixture by selectively removing undesired molecules.
Gene: A region of DNA that carries information that controls a
particular biochemical process.
Gene probe: A labeled fragment of DNA used to find and characterize
genes within the total DNA of an organism, or to determine the presence of particular DNA
sequences in a mixture.
Genetic map: A line that displays the relative location and order of
genes and other genetic elements on a chromosome.
Genetic marker: A readily
identifiable genetic element that exists in two or more allelic forms and is inherited in
association with particular genes and genetic traits of interest.
Genome: The entire complement of genetic material in
the egg or sperm of an animal.
Genotype: The genetic makeup of an individual.
Heterozygote: An animal that possesses two different forms, or
alleles, of a genetic unit; one allele is derived from the mother and the other from the
father.
Homozygote: An animal that possesses two doses of the same allele of
a genetic unit, one from its mother and the other from its father.
Locus: A general term for a region (or "location") along a
length of DNA or chromosome where a genetic unit is found; the term can refer to something
as simple as a single base or as complex as an entire gene.
Marker assisted selection: The use of genetic markers to identify
animals that carry genes for desirable (or undesirable) traits, so that those animals can
be used (or avoided) as brood stock in a selective breeding program.
Microsatellite (Marker): A type of genetic marker that consists of
numerous repeats of short sequences of DNA bases. Microsatellites are currently the marker
of choice for population studies, selective breeding, etc., because they are found at loci
throughout the animal’s DNA and have a likelihood of being highly polymorphic (see
below).
Nucleotides: The building blocks of DNA. A nucleotide contains a base
as a portion of its structure. There are four kinds of bases, so there are four kinds of
nucleotides.
PCR (Polymerase chain reaction): A method of producing relatively
large amounts of specific regions of DNA, thereby making possible various analyses that
are based on those regions.
PCR primer: Relatively short fragments of single-stranded DNA used in
the PCR amplification of specific regions of DNA.
Phenotype: The distinguishable characteristic(s) of a genetically
controlled trait.
Polymorphism: The presence in a population of two or more different
forms of a gene, genetic marker, or inherited trait.
RAPD (Randomly amplified polymorphic DNA): A source of often
polymorphic DNA fragments generated in a PCR-like reaction.
RFLPs (Restriction fragment length polymorphisms): A type of genetic
marker based on differences in the length of DNA fragments when the DNA is cut into
fragments by specialized enzymes called restriction endonucleases. RFLPs provide an
effective form of molecular marker, but are relatively difficult to find and characterize.
Selective breeding: A program of breeding that uses animals that
possess or display desirable traits as parents.
SSRs (Simple sequence repeats): Synonymous with
"microsatellites."
STRs (Short tandem repeats): Synonymous with
"microsatellites." |
