Question 1

Which of the following best describes a loss-of-function mutation?

Accepted Answer

A mutation that reduces or eliminates the activity of the gene product.

Question 2

A patient with the Bombay phenotype has which of the following characteristics?

Accepted Answer

They lack the H substance required for A and B antigen synthesis.

Question 3

Which equation correctly represents the expected phenotypic ratio in the F2 generation of a monohybrid cross showing incomplete dominance?

Accepted Answer

$$1:2:1$$

Question 4

In the context of epistasis, which scenario best illustrates recessive epistasis?

Accepted Answer

A homozygous recessive genotype at one locus prevents the expression of alleles at a second locus.

Question 5

Which of the following statements about codominance is correct?

Accepted Answer

Both alleles in a heterozygote are fully expressed, as seen in the human ABO blood group.

Question 6

A geneticist observes that two mutations causing similar phenotypes in Drosophila complement each other when crossed. What does this indicate?

Accepted Answer

The mutations are in different genes.

Question 7

Which of the following best defines pleiotropy?

Accepted Answer

A single gene influences multiple phenotypic traits.

Question 8

A woman who is heterozygous for the X-linked red/green color blindness allele has children with a man who is not color blind. What is the probability that their son will be color blind?

Accepted Answer

$$0.5$$

Question 9

Which of the following is an example of a temperature-sensitive mutation affecting phenotype?

Accepted Answer

Siamese cats having darker fur on cooler areas of their bodies.

Question 10

Which of the following best describes penetrance?

Accepted Answer

The percentage of individuals with a given genotype who express the associated phenotype.

Question 11

A mutation that does not change the amino acid sequence of a protein is called:

Accepted Answer

Silent mutation

Question 12

Which of the following is true about dominant lethal alleles?

Accepted Answer

They are always expressed in the heterozygous state and often result in death before reproductive age.

Question 13

Which of the following best describes the concept of epigenesis?

Accepted Answer

An organism develops from a fertilized egg through a series of developmental events.

Question 14

Which of the following is an example of a nutritional mutation in humans?

Accepted Answer

Phenylketonuria, which requires a low-phenylalanine diet to prevent symptoms.

Question 15

Which of the following best explains why carriers of Tay-Sachs disease do not develop symptoms?

Accepted Answer

Carriers produce enough beta-hexosaminidase A enzyme to prevent GM2 ganglioside accumulation.

Question 16

Which of the following is a real-world example of codominance?

Accepted Answer

AB blood type in humans, where both A and B antigens are expressed.

Question 17

Which of the following best describes the effect of genetic background on phenotypic expression?

Accepted Answer

The physical location of a gene can influence its expression due to chromosomal rearrangements.

Question 18

In summer squash, which genotype results in disc-shaped fruit?

Accepted Answer

$$AABB$$

Question 19

Which of the following best describes sex-influenced inheritance?

Accepted Answer

The expression of a trait is affected by the sex of the individual, but not limited to one sex.

Question 20

Which of the following is an example of a multi-step genetic interaction resulting in a novel phenotype?

Accepted Answer

Disc-shaped fruit in summer squash requiring dominant alleles at two loci.

Extensions of Mendelian Genetics: Mechanisms and Phenotypic Outcomes

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