TTU Breeding and Genetics Final

Genetics

the science of heredity

Animal Breeding

the application of scientific knowledge to make genetic improvement in animals.

Germ Plasm

any form of genetic material (ie. semen, oocytes, embryos, or live animals)

Seedstock Operation

a breeding program which produces animals intended to be parents (seedstock = breeding stock)

Commercial Operation

a breeding program which produces a commodity which is consumed by the public

Natural Selection

random mating of animals in nature independent of man's control

Artificial Selection

human intervention process whereby parents are chosen and the extent of their prolificacy is controlled.

Breeding Objective

a goal focused on attainment of the most ideal traits(s) for the breeding program or production system

Breeding Program

selection of the most desirable animals for propagation of offspring which best target the breeding objective.

Phenotype

an observable or quantifiable expression of a trait (ie. red, 80 lb. BW, etc.)

Genotype

the genetic makeup of an individual

Environment

all non-genetic factors which influence phenotype (ie. nutrition, health, weather, etc.)

Qualitative Trait

a categorical trait which can not be measured and is generally controlled by only one or a few genes (also called a simply inherited trait)

Quantitative Trait

a continuous trait which can be measured and is controlled by numerous additive genes

Codon

a sequence of three nucleotides

which translates to a specific amino acid, or, a "stop" or "start" command for construction of the

amino acid chain (ie. promoter)

DNA

an information storage molecule

essential to all living organisms regardless if

we are speaking about prokaryotic or

eukaryotic organisms

MRNA

RNA polmerase and one strand of DNA. Messenger RNA

Transcription

the process by which RNA polymerase

uses one strand of DNA to assemble mRNA

Transcription Factors

proteins which act as modulators of the transcription process

Translation

the process by which mRNA is used to synthesize protein

TRNA

transcription RNA; the molecules that

actually achieve the "translation" between the

two languages

Gene

is the basic unit of heredity

DNA Replication

When DNA is to be replicated, a set of proteins binds to

the DNA, and begins to separate the strands

Mutation

a heritable genetic change, either for better or worse

Mutagens

Environmental substances which interact with DNA (ex.

chemicals or radiation) to cause mutations

Genome

- the entire set of genes in an organism's DNA

Chromosome

is a single, supercoiled strand of DNA, held together by structural proteins

Homolog Chromosome

one of a pair of chromosomes having

corresponding loci

Karotype

is a process by which DNA is isolated from blood and chromosomes are visualized

Mitosis

type of cell division that results in two new diploid daughter cells

Meiosis

generates four

haploid daughter cells which each contains

unique genetic information

Synapsis

an extended period of time the replicated

homologous chromosome line up alongside each other

Tetrad

pairing of homologus chromosomes

Crossing Over

where specific enzymes cut the

DNA of each homologue, and a reciprocal exchange of

DNA segments occurs

Loci

a specific location of a gene on a chromosome

Allele

is an alternative form of a gene (ie. B =

black & b = red); there may be two allele

possibilities or multiple allele possibilities for a

gene

Zygote

is a one celled (2n) embryo formed from the union of male and female gametes

Sex Linked Inheritance

is the inheritance pattern of genes located on the sex chromosome

Sex Limited Inheritance

is the inheritance of a trait which can only be physically expressed in one sex

Ex. milk production, semen quality, and egg production

Sex Influenced Inheritance

are traits that can be expressed in both sexes, but the rules of inheritance differ between sexes

Ex. the allele for scurs is dominant in male cattle but recessive in female cattle

Law of Segregation

during meiosis only one gene per loci in the diploid parent cell separates to form the haploid gamete cell

Law of Independent Assortment

genes separate at random and independent of one

another

Linkage

loci of interest which are close together on the same chromosome

Homozygous

identical alleles at corresponding loci

Heterozygous

different alleles at corresponding loci

Complete Dominance

a form of dominance in which the phenotype of the heterozygote genotype is identical to the homozygous

dominant phenotype

Incomplete Dominance

an interaction where the heterozygote phenotype is intermediate to

that of the homozygous dominant and

recessive phenotypes (doesn't necessarily

mean exactly midway)

No Dominance

a condition in which neither allele shows dominance and the heterozygote

phenotype is exactly midway between the

homozygous phenotypes

Over Dominance

a condition in which the heterozygote genotype expresses a phenotype

outside the range of the homozygous

phenotype

Epistasis

interaction between genes at different loci

Gene Frequency

the relative frequency of a specific gene (or allele)

in a population

Genotypic Frequency

the relative frequency of a specific genotype at a

single locus in a population

Fixation

the point at which a specific allele

becomes the only one present at a locus in the

entire population; therefore the gene's

frequency is one

Hardy Weinburg Equilibrium

a state of constant gene and genotypic frequencies in a

population when forces which can alter these

frequencies are absent (the population must

be large and randomly mated)

Test Mating

a mating specifically designed to reveal the true

genotype of a parent at a specific locus or a

few loci

Fitness

the contributing number of offspring and a

given genotype an individual produces for the next

generation

Dominance

interaction between genes at the

same locus

Genotypic Value

the value of an individual's

genes to its own performance

Breeding Value

the value of an individual's

genes to its progeny's performance

Gene Combination Value

The part of an individual's genotypic value that is due to

the effects of gene combinations (dominance

and epistasis) and cannot, therefore, be

transmitted from parent to offspring

EPD

expected progeny differences

Repeated Trait

a trait for which animals have

more than one performance record (ie. milk

production in dairy species, wool production,

racing times in horses, etc.

Temporary Environmental Effect

an

environmental effect which influences a single

performance record but not all the animal's

performances for a repeated trait

Permanent Environmental Effect

an

environmental effect which permanently

influences an animal's performance for a

repeated trait

Heritability in the Broad Sense

a measure of the strength

of performance and genotypic values for a

trait in a population

Heritability in the Narrow Sense

a measure of the strength of

performance and breeding values for a trait in

a population

Repeatability

a measure of the strength of

the relationship between phenotypes for a

repeated trait in a population

Contemporary Group

a contemporary group is a group of

animals which are similar in sex and age and have been

treated alike

Accuracy of Selection

a measurement of the

strength of the relationship between the TRUE

breeding value and a PREDICTION of the breeding

value for a given trait under selection

GE-EPD

Genomic Enhanced Expected Progeny Differences; includes the genotypic information generated by

the HD50K test into the existing calculation of EPDs

Genetic Variation

the amount of variation in

breeding values within a population for a given trait

under selection (ie. the standard deviation of the

entire population of potential parents)

Generation Interval

the amount of time

required to replace one generation with the next

Selection Differential

the difference between

the mean selection criterion of those individuals

selected to be parents and mean selection

criterion of the entire population of potential

parents (it is expressed in the units of the

selection criterion)

Selection Intensity

a measurement of how

"picky" animal breeders are when deciding

which individuals are selected to breed

Large Scale Genetic Evaluation

the

genetic evaluation of large populations;

typically entire breeds within a country or

region

Central Test

a test designed to evaluate the

performance of young males from different herds

or flocks for growth traits by feeding them a

common diet at a central location

Parent EPD

an EPD and the associated accuracy

for an animal with progeny data

Non

Parent EPD - an EPD (generally without an

accuracy value) for an animal without progeny

data

Pleiotropy

he occurrence of a single gene

affecting more than one trait

Genetic Correlation

the correlation

in breeding values of two different traits

Curvebender

When two traits are opposite of eachother. ie. Low BW high WW

Indicator Trait

a trait that may or may

not be relevant itself but is utilized to improve

a genetically correlated trait of interest

Multiple Trait Selection

election for

more than one trait

Aggregate Breeding Value

the

breeding value for a combination of traits

Tandem Selection

election for one trait and

then another

Independent Culling Levels

minimum

standards are set for multiple traits and individuals

which don't meet or exceed the standards set for all

traits are culled

Economic Selection Index

a multi-trait

index which combines economically relevant traits

and associated weighting factors to assess the

aggregate breeding value of an individual in

economic terms

Random Mating

animals which are mated at

random

Positive Assortative Mating

a mating

strategy based upon mating similar animals

Negative Assortative Mating

a mating

strategy based upon mating dissimilar (dissimilar

for whatever the traits(s) of interest are)

Corrective Mating

designed to correct in

their progeny faults of one or both of their

parents

Inbreeding

the mating of individuals which are related (ie. they share a common ancestor)

Prepotency

the ability to consistently pass on

similar character and type to their progeny

Inbreeding Coefficient

an estimate of the

proportion of gene pairs in an animal which are

identical by descent (ie. a measurement of the

degree of inbreeding in an animal)

Wright's Relationship Coefficient

an

estimate of the proportion of an animal's genes

which are identical by descent to another animal's

genes (ie. a measurement of pedigree relationship

between two animals)

Common Ancestor

an individual which appears on

both paternal and maternal sides of a pedigree

Inbreeding Depression

Linebreeding

is a mild form of inbreeding in

which generally only one animal is replicated

in an animal's pedigree many times because

they are thought to be superior

Outbreeding

the mating of unrelated individuals (ie. they DO NOT share a common ancestor

Crossbreeding

is the mating of individuals of different breeds