Question 1

A pea plant with genotype $$YyRr ($$where Y = yellow, y = green, R = round, r = wrinkled) is crossed with another plant of genotype $$yyrr. $$What is the expected phenotypic ratio in the offspring?

Accepted Answer

1 yellow round : 1 yellow wrinkled : 1 green round : 1 green wrinkled

Question 2

Which of the following best describes a heterozygous genotype?

Accepted Answer

Both alleles are different for a given gene

Question 3

During which stage of meiosis do homologous chromosomes separate?

Accepted Answer

Anaphase I

Question 4

If a cell has 8 chromosomes at the start of G1, how many DNA molecules and chromosomes will it have at the end of S phase?

Accepted Answer

8 chromosomes, 16 DNA molecules

Question 5

Which of the following is true about sister chromatids?

Accepted Answer

They are identical copies of a chromosome joined at the centromere

Question 6

In a dihybrid cross between two heterozygotes ($$AaBb 	imes AaBb$$), what is the expected phenotypic ratio if the genes assort independently?

Accepted Answer

$$9:3:3:1$$

Question 7

A woman who is a carrier for hemophilia (an X-linked recessive disorder) marries a normal man. What is the probability that their son will have hemophilia?

Accepted Answer

$$0.25$$

Question 8

Which type of epistasis results in a $$9:7$$ phenotypic ratio in the F2 generation?

Accepted Answer

Duplicate recessive epistasis

Question 9

If a cell in metaphase II of meiosis contains 12 chromosomes, how many chromosomes will each gamete have after meiosis is complete?

Accepted Answer

6

Question 10

Which of the following best describes homologous chromosomes?

Accepted Answer

They carry the same genes but may have different alleles

Question 11

A geneticist observes a $$12:3:1$$ phenotypic ratio in the F2 generation of a cross. Which type of epistasis is most likely involved?

Accepted Answer

Dominant epistasis

Question 12

Which stage of the cell cycle is characterized by DNA replication?

Accepted Answer

S phase

Question 13

A man with genotype $$X^AY ($$normal vision) and a woman with genotype $$X^AX^a ($$carrier for color blindness) have a daughter. What is the probability that she will be color blind?

Accepted Answer

$$0$$

Question 14

Which of the following is NOT a difference between mitosis and meiosis?

Accepted Answer

Mitosis reduces chromosome number by half; meiosis maintains chromosome number

Question 15

In a population with three alleles ($$A_1$$, $$A_2$$, $$A_3) at a $$single gene locus, how many possible genotypes can exist?

Accepted Answer

9

Question 16

Which of the following best describes non-sister chromatids?

Accepted Answer

They are chromatids from homologous chromosomes

Question 17

A woman with blood type $$IAi$$ and a man with blood type $$IBi$$ have a child. What is the probability that the child will have blood type AB?

Accepted Answer

$$0.25$$

Question 18

Which of the following is a real-life example of a trait controlled by genes on sex chromosomes?

Accepted Answer

Hemophilia

Question 19

If a cell at metaphase of mitosis contains 20 chromosomes, how many chromosomes will each daughter cell have after cytokinesis?

Accepted Answer

20

Question 20

Which of the following best explains why the phenotypic ratio in a monohybrid cross between two heterozygotes is $$3:1$$?

Accepted Answer

The dominant allele masks the effect of the recessive allele

Classical Genetics: Core Concepts and Analytical Skills

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