All Free Veterinary Science MCQs with Answers

• A. Additive genetic variance
• B. Dominance genetic variance
• C. Permanent environmental variance
• D. Temporary environmental variance

Explanation: Narrow-sense heritability is additive genetic variance divided by phenotypic variance.

• A. Identical by mutation
• B. Identical by descent
• C. Different in origin
• D. Dominant in expression

Explanation: The inbreeding coefficient is the probability that the two alleles inherited by an individual are identical by descent.

• A. Performance of the older parent breed
• B. Performance of the poorer parent breed
• C. Average performance of its parent breeds
• D. Average performance of unrelated purebreds

Explanation: Heterosis, or hybrid vigour, is commonly calculated by comparing crossbred performance with the average of the two parental breed…

• A. Pedigree recording
• B. Mass selection
• C. Phenotypic grading
• D. Progeny testing

Explanation: Progeny testing evaluates a sire by studying the performance of many offspring produced with different dams.

• A. 25 percent
• B. 50 percent
• C. 75 percent
• D. 100 percent

Explanation: A carrier by carrier mating has expected genotypes of 25 percent affected homozygotes, 50 percent carriers, and 25 percent normal…

• A. 0.5 units
• B. 1 unit
• C. 4 units
• D. 16 units

Explanation: The response is calculated as R = h² × S. Therefore, R = 0.25 × 4 = 1 unit, assuming the heritability and selection differential are…

• A. 54
• B. 60
• C. 64
• D. 78

Explanation: Domestic cattle have a diploid chromosome number of 60, arranged in 30 pairs.

• A. Only sex-linked variance
• B. Only mutation variance
• C. Only temporary environment
• D. Additive genetic variance

Explanation: Repeatability includes additive genetic effects and permanent environmental effects that continue to influence repeated records.

• A. Males are ZZ and females are ZW
• B. Males are ZW and females are ZZ
• C. Males are XX and females are XY
• D. Males are XY and females are XX

Explanation: Birds generally have ZZ males and ZW females. Thus, the female is the heterogametic sex because her eggs carry either a Z or a W chromosome.

• A. 21 percent
• B. 30 percent
• C. 42 percent
• D. 49 percent

Explanation: The recessive phenotype frequency is q² = 0.09, so q = 0.3 and p = 0.7. The carrier frequency is 2pq = 2 × 0.7 × 0.3 = 0.42, or 42 percent.

• A. Epistatic gene effect
• B. Dominance gene effect
• C. Additive gene effect
• D. Environmental effect

Explanation: Additive gene effects are the average effects of individual alleles and are transmitted predictably to progeny.

• A. Extra chromosome copies
• B. New alleles by mutation
• C. Different alleles at each locus
• D. Identical alleles by descent

Explanation: Related parents are more likely to carry copies of the same ancestral allele.

• A. Daughters
• B. Parents
• C. Siblings
• D. Mating partners

Explanation: A dairy sire is commonly evaluated through the milk production of many daughters because daughters inherit half of their genes from him.

• A. Heritability
• B. Repeatability
• C. Genetic correlation
• D. Phenotypic variance

Explanation: Repeatability is the correlation between repeated records of the same trait in an individual.

• A. Complete dominance
• B. Independent assortment
• C. Genetic linkage
• D. Random mutation

Explanation: Genes positioned close together on one chromosome tend to be inherited together, a phenomenon called genetic linkage.

• A. Three quarters dominant and one quarter recessive
• B. Half recessive and half dominant
• C. All phenotypically recessive
• D. All phenotypically dominant

Explanation: The bull produces dominant and recessive gametes, while the homozygous dominant cow produces only dominant gametes.

• A. Crossbreeding
• B. Close breeding
• C. Pure breeding
• D. Random mating

Explanation: Crossbreeding combines desirable characteristics from different breeds and can produce heterosis in the crossbred progeny.

• A. All animals breed equally
• B. The sex ratio is unequal
• C. Mating is completely random
• D. Generations overlap equally

Explanation: An unequal number of breeding males and females reduces the effective population size because fewer individuals contribute genes equally…

• A. Both sexes equally
• B. Female offspring
• C. Male offspring
• D. Only maternal offspring

Explanation: Males receive their single X chromosome from their mother, so sons who inherit the recessive allele are affected.

• A. Generation interval
• B. Phenotypic record
• C. Selection differential
• D. Estimated breeding value

Explanation: Estimated breeding value predicts the additive genetic merit that an animal can transmit to its offspring.