Question 1

In a classic Mendelian monohybrid cross between two heterozygous tall pea plants (Dd x Dd), what is the expected phenotypic ratio in the F2 generation?

Accepted Answer

$$3:1$$

Question 2

Which of the following best describes incomplete dominance?

Accepted Answer

The heterozygote expresses a phenotype intermediate between the two homozygotes.

Question 3

A cross between two pink snapdragon flowers (incomplete dominance, R = red, r = white) produces offspring in what phenotypic ratio?

Accepted Answer

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

Question 4

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

Accepted Answer

ABO blood group system

Question 5

If a gene has three alleles (A, B, O) and an individual is genotype AO, what is their blood type?

Accepted Answer

Type A

Question 6

A lethal allele is one that:

Accepted Answer

Can cause death when present in a specific genotype

Question 7

In the agouti mouse coat color system, the $$A^Y$$ allele is dominant for yellow color but recessive lethal. What is the expected phenotypic ratio in the offspring of a cross between two yellow mice ($$A^Y A x$$ $$A^Y A$$)?

Accepted Answer

$$1$$ agouti : $$2$$ yellow

Question 8

Which of the following best explains why reciprocal crosses for X-linked traits yield different results?

Accepted Answer

Males are hemizygous for X-linked genes.

Question 9

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

Accepted Answer

Type A or Type B

Question 10

Which genetic phenomenon is illustrated by the Bombay phenotype, where an individual with genotype $$hh$$ does not express the ABO blood group antigens?

Accepted Answer

Epistasis

Question 11

In a dihybrid cross involving two independently assorting genes with complete dominance, what is the expected phenotypic ratio in the F2 generation?

Accepted Answer

$$9:3:3:1$$

Question 12

Which of the following is true about gene interactions known as complementation?

Accepted Answer

One dominant allele of each gene is required for the phenotype.

Question 13

A cross between two plants produces offspring in a $$9:7$$ ratio. Which gene interaction is most likely responsible?

Accepted Answer

Complementation

Question 14

Which of the following best describes polygenic inheritance?

Accepted Answer

Multiple genes, each with small additive effects, control a trait.

Question 15

If a trait is determined by two genes with redundancy, what is the expected phenotypic ratio in the F2 generation?

Accepted Answer

$$15:1$$

Question 16

Which of the following is a key assumption of classical Mendelian genetics that is often modified in extensions?

Accepted Answer

Alleles segregate independently during gamete formation.

Question 17

A cross between two heterozygotes for a gene with incomplete dominance results in what genotypic ratio?

Accepted Answer

$$1:2:1$$

Question 18

Which of the following best describes the molecular basis of incomplete dominance?

Accepted Answer

One allele is a loss-of-function allele, resulting in a dosage effect.

Question 19

In a case of dominant epistasis, what is the expected phenotypic ratio in the F2 generation?

Accepted Answer

$$12:3:1$$

Question 20

Which of the following is true about the relationship between genotype and phenotype in codominance?

Accepted Answer

The heterozygote expresses both parental phenotypes equally.

Extensions of Mendelian Genetics: Modified Inheritance Patterns and Gene Interactions

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