Question 1

Which of the following best describes the principle of independent assortment as demonstrated by Mendel’s dihybrid cross?

Accepted Answer

Alleles for different genes segregate independently during gamete formation.

Question 2

A cross between two heterozygous individuals for two independently assorting genes (AaBb x AaBb) produces which phenotypic ratio in the F2 generation?

Accepted Answer

$$9:3:3:1$$

Question 3

If an organism is heterozygous for three independently assorting gene pairs, how many different types of gametes can it produce?

Accepted Answer

$$2^3 = 8$

Question 4

Which of the following is an example of incomplete dominance?

Accepted Answer

A cross between red and white snapdragons producing all pink offspring.

Question 5

In the ABO blood group system, which genotype(s) can produce an individual with type O blood?

Accepted Answer

$$ii$$

Question 6

A woman with blood type O has a child with blood type AB. Which genetic phenomenon best explains this observation?

Accepted Answer

Epistasis due to the Bombay phenotype

Question 7

Which of the following best describes a null allele?

Accepted Answer

An allele that results in complete loss of gene function

Question 8

A cross between two yellow mice (heterozygous for the yellow allele, which is dominant to agouti but lethal when homozygous) produces which phenotypic ratio among surviving offspring?

Accepted Answer

$$2/3$$ yellow : $$1/3$$ agouti

Question 9

Which of the following is an example of pleiotropy?

Accepted Answer

A single gene mutation causing multiple symptoms in Marfan syndrome

Question 10

Which of the following best describes recessive epistasis?

Accepted Answer

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

Question 11

In a dihybrid cross involving two genes with recessive epistasis, what is the expected phenotypic ratio in the F2 generation?

Accepted Answer

$$9:3:4$$

Question 12

Which of the following is true about codominance?

Accepted Answer

Both alleles are fully expressed in the heterozygote

Question 13

A man with type AB blood and a woman with type O blood have children. What are the possible blood types of their children?

Accepted Answer

Type A or type B

Question 14

Which of the following best explains the phenomenon of genetic anticipation?

Accepted Answer

A genetic disorder appears at an earlier age and with increased severity in successive generations

Question 15

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

Accepted Answer

A mutation that causes a phenotype only at high or low temperatures

Question 16

Which of the following best describes penetrance?

Accepted Answer

The percentage of individuals with a given genotype who show the expected phenotype

Question 17

A cross between two plants produces offspring with a 9:7 phenotypic ratio. Which genetic interaction is most likely responsible?

Accepted Answer

Complementary gene action

Question 18

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

Accepted Answer

A phenotype is only expressed in one sex, even though both sexes carry the gene

Question 19

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

Accepted Answer

Other genes in the genome can modify the expression of a mutant phenotype

Extensions and Modifications of Mendelian Genetics: Study Notes

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