OAT Genetics and Evolution

Question 1

Which of the following best describes the law of independent assortment?

Accepted Answer

Genes on different chromosomes are inherited independently of one another

Answer

Mendel's law of independent assortment states that alleles of genes located on different (non-homologous) chromosomes segregate independently during gamete formation.

Question 2

A woman who is a carrier for an X-linked recessive disorder mates with an unaffected man. What is the probability that their son will be affected?

Accepted Answer

50%

Answer

A carrier mother (X^A X^a) passes either X^A or X^a to sons with equal probability; sons receiving X^a will be affected, giving a 50% chance.

Question 3

Which type of mutation results in a premature stop codon?

Accepted Answer

Nonsense mutation

Answer

A nonsense mutation changes a codon that encodes an amino acid into a stop codon (UAA, UAG, or UGA), causing premature termination of translation.

Question 4

In a testcross, an individual with an unknown genotype for a single trait is crossed with a:

Accepted Answer

Homozygous recessive individual

Answer

A testcross uses a homozygous recessive individual so that only the gametes of the unknown-genotype parent determine the offspring phenotype ratio.

Question 5

Which of the following is an example of codominance?

Accepted Answer

AB blood type in humans expressing both A and B antigens

Answer

Codominance occurs when both alleles are fully and simultaneously expressed; AB blood type is the classic example because both A and B antigens appear on red blood cells.

OAT - Optometry Admission Test Practice Test

OAT - Optometry Admission Test Practice Test

OAT Genetics and Evolution