Question 1

Which of the following best describes incomplete dominance?

Accepted Answer

The heterozygote expresses a phenotype intermediate between the two homozygotes.

Question 2

A cross between two pink-flowered snapdragons (where red is $$RR$$, white is $$rr$$, and pink is $$Rr) $$produces offspring in what phenotypic ratio?

Accepted Answer

$$1$$ red : $$2$$ pink : $$1$$ white

Question 3

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

Accepted Answer

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

Question 4

A mutation that results in a nonfunctional gene product and is only lethal in the homozygous state is called:

Accepted Answer

Recessive lethal allele

Question 5

Which of the following best defines pleiotropy?

Accepted Answer

A single gene affects multiple phenotypic traits.

Question 6

In the context of gene interaction, what is epistasis?

Accepted Answer

The expression of one gene masks or modifies the expression of another gene.

Question 7

A woman with genotype $$I^A I^B$$ for the ABO blood group and a man with genotype $$I^B i$$ have a child. What is the probability that the child will have blood type B?

Accepted Answer

$$1/2$$

Question 8

Which of the following statements about wild-type alleles is correct?

Accepted Answer

Wild-type alleles are the most common alleles in a population and are used as a standard for comparison.

Question 9

A patient is diagnosed with Tay-Sachs disease, which is caused by a deficiency in Hexosaminidase A. What type of allele is responsible for this condition?

Accepted Answer

Recessive lethal allele

Question 10

Which of the following best explains why alleles exist in populations?

Accepted Answer

Alleles arise due to errors in DNA replication, transcription, translation, and environmental influences.

Question 11

A gene that, when mutated, results in death is called:

Accepted Answer

Essential gene

Question 12

In a population, the frequency of the sickle cell allele ($$S) is$$ $$0.1. $$Assuming Hardy-Weinberg equilibrium, what is the expected frequency of individuals homozygous for the sickle cell allele ($$SS$$)?

$$	ext{Frequency of } SS = q^2$

Accepted Answer

$$0.01$$

Question 13

Which of the following is an example of a dominant lethal allele in humans?

Accepted Answer

Huntington's disease

Question 14

If a gene has three alleles ($$A$$, $$B$$, $$C) in a $$population, how many possible genotypes can be formed at this locus?

Accepted Answer

$$6$$

Question 15

Which of the following best describes polygenic inheritance?

Accepted Answer

Multiple genes contribute to a single phenotypic trait.

Question 16

A man with blood type AB ($$I^A I^B) $$and a woman with blood type O ($$ii) $$have children. What are the possible blood types of their children?

Accepted Answer

A and B only

Question 17

Which of the following is true about gene linkage?

Accepted Answer

Linked genes are inherited together because they are located close to each other on the same chromosome.

Question 18

In the agouti gene system in mice, the $$A$$ allele (yellow) is dominant over $$a ($$black). However, the $$A$$ allele is also a recessive lethal. What is the expected phenotypic ratio in the offspring of two yellow mice ($$A/a$$)?

Accepted Answer

$$2$$ yellow : $$1$$ black

Question 19

Which of the following best describes a null allele?

Accepted Answer

An allele that produces no functional product.

Question 20

A person with sickle cell trait ($$HbA/HbS) $$produces both normal and sickle hemoglobin. This is an example of:

Accepted Answer

Codominance at the molecular level

Extensions of Mendelian Genetics: Key Concepts and Patterns

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