Question 1

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

Accepted Answer

A mutation that causes a reduction or elimination of the normal activity of the gene product

Question 2

In Drosophila, the wild-type body color is gray and is represented by $$e^+$$, while the ebony mutant is represented by $$e. $$What is the genotype of a gray heterozygote?

Accepted Answer

$$e^+/e$$

Question 3

A red snapdragon ($$C^R C^R) is $$crossed with a white snapdragon ($$C^W C^W). $$What is the expected phenotypic ratio in the F2 generation?

Accepted Answer

$$1/4$$ red, $$1/2$$ pink, $$1/4$$ white

Question 4

Which of the following statements about codominance is correct?

Accepted Answer

Both alleles are fully expressed in the heterozygote

Question 5

In the human ABO blood group system, which genotype will result in blood type AB?

Accepted Answer

$$I^A I^B$$

Question 6

A mutation in an essential gene that is only lethal when homozygous is called a:

Accepted Answer

Recessive lethal allele

Question 7

A man with Huntington disease (autosomal dominant) has children with a woman who does not carry the allele. What is the probability that their child will inherit the disease?

Accepted Answer

$$1/2$$

Question 8

Which of the following best describes epistasis?

Accepted Answer

The expression of one gene is modified or masked by another gene

Question 9

In the Bombay phenotype, individuals with the genotype $$hh do $$not express A or B antigens, even if they have $$I^A or$$ $$I^B$$ alleles. This is an example of:

Accepted Answer

Recessive epistasis

Question 10

A cross between two heterozygous summer squash plants ($$AaBb) $$produces offspring with a phenotypic ratio of 9 disc: 6 sphere: 1 long. What genetic interaction does this illustrate?

Accepted Answer

Epistasis with novel phenotypes

Question 11

Which of the following is an example of pleiotropy?

Accepted Answer

A gene that affects both connective tissue and vision, as in Marfan syndrome

Question 12

Which of the following best describes X-linkage?

Accepted Answer

Genes located on the X chromosome that show unique inheritance patterns

Question 13

A woman who is a carrier for red-green color blindness (X-linked recessive) has children with a man with normal vision. What is the probability that their son will be color blind?

Accepted Answer

$$1/2$$

Question 14

Which of the following is true about sex-influenced inheritance?

Accepted Answer

The expression of a trait is affected by the sex of the individual, but can be seen in both sexes

Question 15

A genetic disorder shows increased severity and earlier onset in each successive generation. This phenomenon is called:

Accepted Answer

Genetic anticipation

Question 16

Which of the following best defines penetrance?

Accepted Answer

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

Question 17

A temperature-sensitive mutation in a virus results in a mutant phenotype at $$37^ aC$$ but a wild-type phenotype at $$25^ aC. $$This is an example of:

Accepted Answer

Conditional mutation

Question 18

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

Accepted Answer

Phenylketonuria (PKU)

Question 19

Which of the following best describes the genetic background effect known as 'position effect'?

Accepted Answer

The physical location of a gene on a chromosome influences its expression

Question 20

A complementation test is used to determine:

Accepted Answer

If two mutations are in the same gene or in different genes

Extensions of Mendelian Genetics: Comprehensive Study Notes

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