Breeding and Genetics Flashcards
generation of gametes for sexual reproduction through meiotic division
gametogenesis
containing only one set of chromosomes, gametes are these
haploid cell
When two gametes (haploid cells) fuse together
Diploid
Animals inherit one set from father and one set from mother
chromosomes
heterozygous
Qq (having different alleles on chromosomes)
homozygous
QQ, qq (having the same alleles on parental chromosomes)
controlled by one, or very few genes and are much easier to predict
qualitative traits (simply inherited traits)
controlled by many loci
polygenic traits
a continuum stating herd distribution and likelihood of a trait
Normal (Bell) Curve
the shape of the normal curve is determined by a measure of the amount of variation in the population
phenotypic standard deviation
phenotypic mean (herd average) is located at the very center of the
x-axis
frequency of the phenotype occurs on the
y-axis
the way alleles interact with each other (dominance, recessive)
gene action
dominant allele completely masks the effects of the recessive allele; in this case the phenotype is identical to that of the dominant
complete dominance
the phenotype of the offspring is somewhere in the middle, more closely resembling the dominant
partial dominance
phenotype of the heterozygote is outside the range of possible phenotypes exhibited by the two parents (more closely related to dominant allele)
over-dominance
no dominance whatsoever
co-dominance gene action
phenotype is exactly intermediate to the two homozygotes (no dominant allele)
additive gene action
chromosomes that determine the sex of the individual
allosomes
pattern of inheritance for sex-related (female/male) genes is referred to as
sex-linked inheritance
traits in which phenotypic expression is limited to one sex
sex-limited traits
phenotypic expression differs among males and females even if the genotype is the same
sex-influenced traits
different loci are also interacting with each other
epistasis
population average (u) + genetic effects (G) + environmental effects (E) =
Phenotype (P)
a measure that indicates what proportion of the observed phenotypes is due to genetics
heritability
growth and stature rates (average daily gain and body weight)
traits with high heritability
EBV
expected breeding value
EPD
expected progeny differential
ETA
estimated transmitting ability
descendants or offspring
progeny
a measure that tells producers how confident they should be in an EBV or EPD estimate
accuracy value
Benefits of moderate inbreeding
Breeding related animals could help to fix favorable alleles within a population, and increase uniformity within a herd.
overuse of inbreeding resulting in detrimental consequences
inbreeding depression
improved performance of progeny compared to parents
heterosis
this system has been developed to maximize the amount of heterosis achieved by each generation
crossbreeding
sires selected for terminal traits, while females are selected for maternal traits (marketed offspring)
terminal cross
pure sires are rotated each generation and mated to crossbred females that are least like their own breed composition (rotate sires)
rotational cross
maternal rotation to produce replacement females with a terminal cross to take full advantage of hybrid vigor (A, B females and A, B, C breeds)
rota-terminal crossbreeding system
