Question 1

Which of the following best describes incomplete dominance?

Accepted Answer

Neither allele is dominant, and the heterozygote displays an intermediate phenotype between the two homozygotes.

Question 2

In snapdragons, red flowers ($$R^1R^1$) crossed with white flowers (R^2$R^2) $$produce pink flowers ($$R^1R^2$). What is the expected phenotype ratio in the F_2$ generation from selfing the F_1$ plants?

Accepted Answer

$$1:2:1 ($$red:pink:white)

Question 3

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

Accepted Answer

MN blood group

Question 4

A person with genotype $$L^ML^N$$ for the MN blood group will have which phenotype?

Accepted Answer

Both M and N glycoproteins on RBCs

Question 5

How many different alleles can exist for a single gene in a population?

Accepted Answer

Any number, depending on mutation and genetic diversity

Question 6

In the ABO blood group system, which genotype(s) will result in blood type O?

Accepted Answer

$$ii$$

Question 7

A recessive lethal allele is characterized by which of the following?

Accepted Answer

It is lethal only when present in the homozygous state.

Question 8

In mice, the $$A^Y$$ allele is dominant for yellow coat color but recessive lethal. What is the expected genotypic ratio among the surviving offspring from a cross between two $$A^YA$$ mice?

Accepted Answer

$$2:1$$ ($$A^YA:AA)$$

Question 9

Which of the following best describes epistasis?

Accepted Answer

One gene masks or modifies the expression of another gene.

Question 10

The Bombay phenotype is an example of which genetic phenomenon?

Accepted Answer

Epistasis

Question 11

In the Bombay phenotype, individuals with genotype $$hh do $$not express A or B antigens even if they have $$I^A or$$ $$I^B$$ alleles. What is the molecular explanation for this?

Accepted Answer

The $$hh$$ genotype prevents the synthesis of the H antigen, which is required as a precursor for A and B antigen formation.

Question 12

A dihybrid cross involving two gene pairs, one showing classic Mendelian inheritance and the other showing epistasis, will yield which type of phenotypic ratio?

Accepted Answer

A modified ratio depending on the type of gene interaction

Question 13

In a cross between two $$AaBb$$ mice, where gene B is epistatic to gene A, what is the expected phenotypic ratio for agouti:black:albino offspring?

Accepted Answer

$$9:3:4$$

Question 14

Which of the following is true about dominant epistasis, as seen in summer squash color?

Accepted Answer

The dominant allele at one locus masks the expression of alleles at a second locus.

Question 15

Complementary gene interaction, as seen in pea flower color, results in which phenotypic ratio in the $$F_2$$ generation?

Accepted Answer

$$9:7$$

Question 16

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

Accepted Answer

Males are hemizygous for X-linked genes.

Question 17

A male Drosophila with a white-eye mutation (X-linked) is crossed with a red-eyed female. What is the expected phenotype of the $$F_1$$ offspring?

Accepted Answer

All females have red eyes, all males have red eyes.

Question 18

Which of the following best defines penetrance?

Accepted Answer

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

Question 19

Which of the following is an example of extranuclear inheritance?

Accepted Answer

Inheritance of mitochondrial DNA mutations

Modification of Mendelian Ratios: Non-Mendelian Inheritance Patterns in Genetics

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