Animal breeding terminology Flashcards

Question

What can Genetic causes of variation be subdivided into

Answer 1

– Additive components | – Non additive components

Answer 2

interactions among genes – Dominance is due to interactions between alleles at the same locus – Epistasis is due to interactions between genes at different loci

Answer 3

``` – Diet – Weather – Health program – Facilities – Management practices ```

Answer 4

• Differences in genotypes of individuals cause genotypic variation, which in turn causes phenotypic variation • Genotype of an individual is fixed at conception and stays the same until death • Genotype of an individual is determined by the parents – One-half of the genes come from each parent • No two individuals have the same genotype (unless identical twins or clones)

Answer 5

Yes – Even for a highly heritable trait, a large amount of the phenotypic variation is due to the environment – h2 of post-weaning gain in cattle = 0.55 or 55% • 45% of the variation in post-weaning gain is due to the environment, even though post-weaning gain is a highly heritable trait

Answer 6

– Found in a strain of Merino sheep – Booroola = mutation in BMP1B receptor gene – (bone morphogenic protein receptor gene – oocyte & ovary granulosa cells) – Lack of signal to limit ovulation to one follicle – This gene increases the ovulation rate and number of lambs born in sheep. • Average number of lambs born per ewe lambing = 2.4 (range = 1 to 6 lambs) • Litter size in heterozygous ewes is increased by about 0.9 lambs.

Answer 7

– Cattle with this gene are extremely heavily muscled. – Double muscling is due to a mutation in the myostatin or growth and differentiation factor (GDF-8) gene – Mutations render the gene inactive, and therefore, unable to regulate muscle fibre deposition – Penotype occurs at a high frequency in some breeds of cattle • Belgian Blue and Peidmontese.

Answer 8

– A gene found in sheep that results in a condition similar to double muscling in cattle. – “Callipyge” comes from the Greek words for “beautiful buttocks”. – Sheep with this gene have extreme muscling in their loins and hind legs. • The gene greatly increases muscling and decreases fat.

Answer 9

– Called so because of the adverse effect of halothane anaesthetic on pigs carrying this gene – Found primarily in the Pietran breed and Pietran crossbreds with a low frequency in most breeds – Causes reduced litter size, reduced growth rate, and reduced carcass length – Also causes increased loin eye area and increased lean% – Biggest disadvantage is that it causes PSE • Pigs with this gene are susceptible to stress and tend to have PSE (pale, soft, exudative) pork.

Answer 10

• Appears to be dominant • Found primarily in purebred or crossbred Hampshire populations – “Hampshire effect” or “Acid meat” • Negative effects on meat pH, water holding capacity, color, drip loss, cooking loss, and processing yield

Answer 11

Are environmental effects that stay the same from one record to the next on an animal – Stay with animal throughout its lifetime – If a cow loses function of one quarter of her udder due to injury, it will influence her milk production in all future lactations • The feeding program used to raise heifers, if extreme (e.g., too much feed or not enough feed) can influence mammary gland development, which becomes a permanent environmental effect – Will influence all future lactations

Answer 12

• Are environmental effects that change from one record to the next on an animal – Cold and snowy winter one year vs. mild winter the next year – Drought one summer vs. normal rainfall the next summer