General Principles of Animal Breeding, Genetics and Reproduction

Question 1

It contributes to individual fitness and to the evolution of animal genetic resources. By definition, these traits are also important to the ability of the animal genetic resource to be sustained in the production environment.

Answer 1

Adaptation traits

Question 2

The effect of an allele on animal performance, independent of the effect of the other allele at a locus. These effects of the two alleles at a locus add up (thus “additive”). Alleles at a locus may have other effects (dominance, epistasis), so that there are not genes that have just “additive” effects and other genes with only “dominance” effects.

Answer 2

Additive genetic effects

Question 3

Additive genetic effects can be inherited; other genetic effects such as dominance and epistasis are the result of allele combinations that are lost between generations. The additive genetic effect that an animal has for a trait is equal to its breeding value.

Answer 3

Additive genetic effects

Question 4

One of a pair, or series of alternative forms of a gene that can occur at a given locus
on homologous chromosomes

Answer 4

Allele

Question 5

Any one of a class of organic compounds containing the amino (NH2) group and
the carboxyl (COOH) group. Amino acids are combined to form proteins.

Answer 5

Amino acids

Question 6

A system for genetic evaluations that estimates breeding values of individual animals (males, females) at the same time. The system uses production data on all known relatives in calculating a genetic evaluation.

Answer 6

Animal model

Question 7

Any individual from which an animal is descended.

Answer 7

Ancestor

Question 8

Any chromosome that is not a sex chromosome.

Answer 8

Autosome

Question 9

The cross produced by mating a first-cross animal back to one of its parent lines
or breeds.

Answer 9

Backcross

Question 10

Either a sub-specific group of domestic livestock with definable and identifiable external characteristics that enable it to be separated by a visual appraisal from other similarly defined groups within the same species or a group for which geographical and/or cultural
separation from phenotypically similar groups has led to the acceptance of its separate identity.

Answer 10

Breed

Question 11

The mean genetic value of an individual as a parent. It can be estimated as the average superiority of an individual’s progeny relative to all other progeny under conditions of random mating.

Answer 11

Breeding value

Question 12

Spindle-fiber attachment region of a chromosome.

Answer 12

Centromere

Question 13

Microscopically observable linear arrangement of DNA in the nucleus of a cell. Chromosomes carry the genes responsible for the determination and transmission of hereditary characteristics

Answer 13

Chromosome

Question 14

Alleles, each of which produces an independent effect in heterozygotes

Answer 14

Co-dominant alleles

Question 15

The mean performance of a line when involved in a cross-breeding system

Answer 15

Combining ability

Question 16

General combining ability is the average
performance when a breed or line is crossed with
two or more other breeds or lines. Specific combining ability is the degree to which the performance of a specific cross deviates from the average general combining ability of two lines.

Answer 16

Combining ability

Question 17

A line that is randomly selected and randomly mated. Usually used in selection experiments to monitor environment effects in order to estimate the genetic change in a selected line.

Answer 17

Control line

Question 18

Matings between animals of different breeds or lines.

Answer 18

Crossbreeding

Question 19

The protoplasm outside a cell nucleus.

Answer 19

Cytoplasm

Question 20

An individual descended from other individuals.

Answer 20

Descendant

Question 21

Deoxyribonucleic acid, the chemical material which carries information to code for a
gene.

Answer 21

DNA

Question 22

Applied to one member of an allelic pair of genes, which has the ability to express itself wholly or largely at the exclusion of the expression of the other allele.

Answer 22

Dominant

Question 23

The aggregate of all the external conditions and influences affecting the life
and development of the organism.

Answer 23

Environment

Question 24

A prediction of a breeding value. See breeding value.

Answer 24

Estimated breeding value

Question 25

When the gene at one locus affects the expression of the gene at another locus.

Answer 25

Epistasis

Question 26

A sequence of DNA that is expressed (transcribed) into RNA, then translated into protein. Adjacent exons may be separated by an intron, which is later removed from the RNA transcript via a splicing mechanism.

Answer 26

Exon

Question 27

Animals resulting from crossing parents from different lines or breeds.

Answer 27

F1

Question 28

Animals resulting from matings among F1 parents.

Answer 28

F2

Question 29

Animals resulting from matings among F2 parents.

Answer 29

F3

Question 30

The mean number of offspring per parent that successfully reproduce.

Answer 30

Family size

Question 31

Individuals having the same male and female parents.

Answer 31

Full sibs

Question 32

A sperm or egg cell containing the haploid (1n) number of chromosomes.

Answer 32

Gamete

Question 33

A functional hereditary unit that occupies a fixed location on a chromosome, has a specific influence on phenotype and is capable of mutation to various allelic forms.

Answer 33

Gene

Question 34

A gene or DNA sequence having a known location on a chromosome and associated with a particular gene or trait; a gene phenotypically associated with a particular, easily identified trait and used to identify an individual or cell carrying that gene.

Answer 34

Genetic marker

Question 35

Variation in phenotype which results from variations in genetic composition among individuals.

Answer 35

Genetic variance

Question 36

The complete set of genes and non-coding sequences present in each cell of an organism, or the genes in a complete haploid set of chromosomes of a particular organism

Answer 36

Genome

Question 37

A discipline in genetics concerned with the study of the genome of an organism. The field includes efforts to determine the entire DNA sequence of organisms and fine-scale genetic mapping.

Answer 37

Genomics

Question 38

It also studies intragenomic phenomena such as heterosis, epistasis, pleiotropy, and other interactions between loci and alleles within the genome.

Answer 38

Genomics

Question 38

The genetic constitution of one or a few gene(s) or locus (loci), or total genetic make-up (genes) of an individual organism.

Answer 38

Genotype

Question 39

The process of repeated backcrossing to one parental line to produce a population that is nearly purebred.

Answer 39

Grade-up

Question 40

Individuals that share only one common parent.

Answer 40

Half sibs

Question 41

A set of alleles at a closely linked group of loci, so closely linked that the allelic set behaves almost as one allele in terms of inheritance.

Answer 41

Haplotype

Question 42

Degree to which a given trait is controlled by inheritance; proportion of total phenotypic variation that is attributable to genetic variation (in contrast to environment-caused variation).

Answer 42

Heritability

Question 43

The degree to which the performance of a crossbred animal is better or worse than the average performance of the parents.

Answer 43

Heterosis

Question 44

An organism with unlike members of any given pair or series of alleles, which consequently produces unlike gametes.

Answer 44

Heterozygote, adj. heterozygous

Question 45

Chromosomes which occur in pairs and are similar in size and shape, one having come from the male and one from the female parent.

Answer 45

Homologous chromosomes

Question 46

An organism whose chromosomes carry identical members of a given pair of genes. The gametes are therefore all alike with respect to this locus.

Answer 46

Homozygote, adj. homozygous

Question 47

Matings among related individuals, which results in progeny that have less heterozygosity and hence more homozygous gene pairs than the average of the population.

Answer 47

Inbreeding

Question 48

When animals are culled if they do not meet all of the minimum levels of performance for a set of traits.

Answer 48

Independent culling

Question 49

The appearance of the metaphase chromosomes of an individual or species, which shows the comparative size, shape, and morphology of the different chromosomes.

Answer 49

Karyotype

Question 50

A gene that results in the death of the animal.

Answer 50

Lethal gene

Question 51

Both internal (e.g., genetic merit) and external (e.g., nutrition, disease, exposure) forces that influence the expression of a threshold character (e.g., disease, conception, abnormalities, etc.).

Answer 51

Liability