Question 1

Which of the following best explains Mendel’s Law of Segregation?

Accepted Answer

Each individual has two alleles for each gene, and these alleles separate during gamete formation so that each gamete receives only one allele.

Question 2

A diploid cell with genotype AaBb undergoes meiosis. Assuming independent assortment and no crossing over, what proportion of the gametes will have the genotype ab?

Accepted Answer

$$\frac{1}{4}$$

Question 3

Which of the following is a molecular explanation for Mendelian complete dominance?

Accepted Answer

The dominant allele produces enough functional protein to mask the effect of the recessive allele.

Question 4

In snapdragons, flower color shows incomplete dominance. If a true-breeding red-flowered plant (RR) is crossed with a true-breeding white-flowered plant (rr), what will be the phenotype ratio in the F2 generation after selfing the F1?

Accepted Answer

1 red : 2 pink : 1 white

Question 5

Which of the following best describes the difference between homologous chromosomes and sister chromatids?

Accepted Answer

Sister chromatids are identical copies formed after DNA replication, while homologous chromosomes are similar chromosomes inherited from each parent.

Question 6

A cross between two yellow mice (genotype $$A^Y a) $$produces a 2:1 ratio of yellow to agouti offspring. What is the most likely explanation for this result?

Accepted Answer

The yellow allele is lethal when homozygous.

Question 7

Which of the following is an example of codominance in humans?

Accepted Answer

ABO blood group, where both $$I^A$$ and $$I^B$$ alleles are expressed in the phenotype of type AB individuals.

Question 8

A Siamese cat has dark fur on its ears, paws, and tail due to a temperature-sensitive allele. What is the best explanation for this phenotype?

Accepted Answer

The enzyme responsible for pigment production is inactive at normal body temperature but active in cooler areas of the body.

Question 9

Which of the following statements about X-linked inheritance is correct?

Accepted Answer

A female must inherit two copies of a recessive X-linked allele to express the trait.

Question 10

Which of the following best describes penetrance?

Accepted Answer

The proportion of individuals with a particular genotype who show the expected phenotype.

Question 11

A human with genotype $$I^A I^B$$ for the ABO blood group will have which blood type?

Accepted Answer

Type AB

Question 12

Which of the following is true about the products of mitosis and meiosis?

Accepted Answer

Mitosis produces two identical diploid cells, while meiosis produces four genetically different haploid cells.

Question 13

Which of the following is an example of a sex-influenced trait?

Accepted Answer

A gene that causes beardedness, which is dominant in males but recessive in females.

Question 14

Which of the following best explains the molecular basis for incomplete dominance?

Accepted Answer

The heterozygote produces half as much functional protein as the homozygous dominant, resulting in an intermediate phenotype.

Question 15

A population of rabbits has four alleles for coat color at the C locus: $$C$$, $$c^{ch}$$, $$c^h$$, and $$c. $$Which genotype would result in a Himalayan phenotype?

Accepted Answer

$$c^h c^h$$

Question 16

Which of the following is an example of pleiotropy?

Accepted Answer

A single gene mutation causing both white fur and deafness in cats.

Question 17

If a trait shows variable expressivity, what does this mean?

Accepted Answer

Individuals with the same genotype may show different severities of the phenotype.

Question 18

Which of the following best describes the outcome of a cross between a red-eyed female fruit fly (X+Xw) and a white-eyed male (XwY), assuming white eyes are X-linked recessive?

Accepted Answer

Half the male offspring will have white eyes, and all female offspring will have red eyes.

Question 19

Which of the following is NOT a modification to simple Mendelian inheritance?

Accepted Answer

Complete dominance with 100% penetrance

Lecture 4

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