All Free Veterinary Science MCQs with Answers

• A. Standardized difference between selected and population means
• B. Proportion of selected animals in the population
• C. Correlation between phenotype and breeding value
• D. Average age of parents when offspring are born

Explanation: Selection intensity expresses how strongly animals are selected by standardizing the selection differential with the phenotypic standard…

• A. Interactions between genes at different loci
• B. Interactions between alleles at the same locus
• C. Environmental differences among management groups
• D. Changes in allele frequency across generations

Explanation: Dominance variance arises when the combined effect of two alleles at one locus differs from the sum of their average effects.

• A. Independent assortment
• B. Crossing over
• C. Mutation
• D. Random mating

Explanation: Mutation changes the DNA sequence and can create a new allele in a population.

• A. The number of generations in its pedigree
• B. The average phenotype of animals in the herd
• C. The age of the candidate at first breeding
• D. A DNA marker linked to a gene affecting the trait

Explanation: Marker-assisted selection uses a genetic marker associated with a quantitative trait locus or another relevant gene.

• A. Offspring used as replacements are born
• B. Selected offspring are born
• C. First offspring are conceived
• D. Last offspring leave the herd

Explanation: Generation interval is commonly defined as the average age of the parents when the offspring that replace them are born.

• A. Unrelated by pedigree for several generations
• B. Similar in phenotype for the selected trait
• C. Different in phenotype for the selected trait
• D. Selected only from a different breed

Explanation: Positive assortative mating pairs phenotypically similar animals, such as high-producing animals with other high-producing animals.

• A. Measured only on a continuous numerical scale
• B. Controlled by one gene with no environmental influence
• C. Expressed in categories after an underlying liability passes a threshold
• D. Observed only when both parents show the same phenotype

Explanation: Threshold traits have an underlying continuous liability, influenced by genes and environment, but the observed outcome is categorical.

• A. Animal's phenotypic record
• B. Genotypic value of its offspring only
• C. Environmental deviation
• D. True breeding value

Explanation: Accuracy measures how closely an estimated breeding value reflects the animal's true additive genetic merit.

• A. 9:3:3:1
• B. 1:1:1:1
• C. 3:1
• D. 1:2:1

Explanation: A dihybrid cross between two heterozygotes gives the classic 9:3:3:1 phenotypic ratio when the loci assort independently and each locus…

• A. Cause no correlated change in the other trait
• B. Cause a correlated decrease in the other trait
• C. Produce an identical increase in the other trait
• D. Remove environmental variation in the other trait

Explanation: A strongly negative genetic correlation means that the additive genetic effects increasing one trait tend to decrease the other.

• A. Twice the estimated breeding value
• B. Equal to the estimated breeding value
• C. One-half of the estimated breeding value
• D. One-quarter of the estimated breeding value

Explanation: Predicted transmitting ability represents the average genetic merit expected to be passed to offspring, so it is approximately one-half of…

• A. Unrelated individual from another breed
• B. Individual from a third unrelated breed
• C. F1 offspring from the same cross
• D. Parent or genetically similar parental type

Explanation: A backcross mates a hybrid or other offspring back to one of its parental types.

• A. Male XY and female XX
• B. Male ZZ and female ZW
• C. Male XX and female XY
• D. Male XO and female XX

Explanation: Most mammals have XX females and XY males. The presence of the Y chromosome, particularly the SRY region, usually initiates male…

• A. A complete chromosome found only in male animals
• B. A chromosome region associated with variation in a measurable trait
• C. A gene that always produces a visible abnormality
• D. A DNA sequence that prevents chromosome replication

Explanation: A QTL is a genomic region containing one or more genes associated with variation in a quantitative trait.

• A. At the same locus on homologous chromosomes
• B. Very close together on the same chromosome
• C. On different chromosomes or far apart on one chromosome
• D. Present only in mitochondrial DNA

Explanation: Genes on different chromosomes generally assort independently during meiosis.

• A. 200 kg
• B. 400 kg
• C. 800 kg
• D. 1,600 kg

Explanation: Expected transmitting ability is approximately one-half of estimated breeding value because offspring receive one allele set from each…

• A. Maternal or sex-linked effects
• B. Only additive gene action
• C. Only environmental temperature
• D. The number of autosomes alone

Explanation: In reciprocal crosses, the parental sexes are reversed. Different results between the two crosses may indicate sex-linked inheritance…

• A. Mating it with a homozygous dominant animal
• B. Mating it with a homozygous recessive animal
• C. Mating it with an unrelated heterozygous animal
• D. Mating it with an animal showing the same phenotype

Explanation: A test cross uses a homozygous recessive partner. Recessive offspring reveal that the dominant-phenotype parent carries the recessive…

• A. Replace all performance records with visual scores
• B. Measure only the feed intake of mature animals
• C. Record pedigrees and maintain breed identity
• D. Prevent the use of artificial insemination

Explanation: Breed registries document pedigrees, parentage, and registration status to maintain the identity and genetic records of a breed.

• A. Chromosome nondisjunction
• B. Complete dominance
• C. Random genetic drift
• D. Genotype by environment interaction

Explanation: Genotype by environment interaction occurs when genotypes respond differently across environments.