Question 1

Which of the following best describes the main difference between the products of mitosis and meiosis in animal cells?

Accepted Answer

Mitosis produces two genetically identical diploid cells, while meiosis produces four genetically different haploid cells.

Question 2

During which phase of the cell cycle does DNA replication occur, and what is the resulting number of chromatids per chromosome at the end of this phase in a human somatic cell?

Accepted Answer

DNA replication occurs during S phase, resulting in two chromatids per chromosome.

Question 3

Which protein complex is responsible for holding sister chromatids together until anaphase, and what enzyme cleaves this complex to allow chromatid separation?

Accepted Answer

Cohesin holds sister chromatids together and is cleaved by separase.

Question 4

A mutation prevents the formation of the synaptonemal complex during meiosis. Which process would be most directly affected?

Accepted Answer

Crossing over between homologous chromosomes during prophase I

Question 5

In a human male, which region of the X and Y chromosomes allows for their pairing during meiosis I?

Accepted Answer

Pseudoautosomal regions (PAR1 and PAR2)

Question 6

Which checkpoint in the cell cycle ensures that all chromosomes are properly attached to the spindle before proceeding to anaphase?

Accepted Answer

Metaphase checkpoint

Question 7

A female cat is heterozygous for an X-linked gene controlling coat color (one allele for black, one for orange). What is the genetic explanation for the calico (patchy) appearance of her fur?

Accepted Answer

Random inactivation of one X chromosome in each cell during early development

Question 8

Which equation correctly represents the DNA content per nucleus at the end of S phase in a human somatic cell, assuming the G1 content is $$x$$ nanograms?

Accepted Answer

$$2x$$

Question 9

A male with an X-linked recessive disorder marries a woman who is a carrier for the same disorder. What is the probability that their son will have the disorder?

Accepted Answer

$$0.25$$

Question 10

Which of the following best explains why X-linked recessive traits are more commonly expressed in males than in females?

Accepted Answer

Males are hemizygous for the X chromosome, so any allele present is expressed.

Question 11

Which mechanism of dosage compensation is used by placental mammals?

Accepted Answer

Random inactivation of one X chromosome in each female somatic cell

Question 12

Which gene is responsible for initiating male sex determination in placental mammals, and on which chromosome is it found?

Accepted Answer

SRY gene on the Y chromosome

Question 13

A cell is observed with chromosomes aligned at the metaphase plate, each chromosome consisting of two sister chromatids. Which phase is this cell in?

Accepted Answer

Metaphase

Question 14

Which of the following events occurs during anaphase I of meiosis but not during anaphase of mitosis?

Accepted Answer

Separation of homologous chromosomes

Question 15

In Drosophila, the X/A ratio determines sex. What would be the expected sex of a fly with two X chromosomes and three sets of autosomes ($$X/A = 2/3$$)?

Accepted Answer

Male

Question 16

Which of the following best describes the role of the XIST gene in X-chromosome inactivation?

Accepted Answer

It produces an RNA that coats and inactivates the X chromosome from which it is transcribed.

Question 17

A geneticist observes a family in which a trait is passed from father to all sons but never to daughters. Which mode of inheritance is most likely?

Accepted Answer

Y-linked

Question 18

Which of the following is a direct mechanical basis for Mendel’s law of segregation during meiosis?

Accepted Answer

Separation of homologous chromosomes during anaphase I

Question 19

In birds, which sex is heterogametic and what is the chromosomal composition?

Accepted Answer

Female, ZW

Question 20

A woman who is heterozygous for an X-linked dominant trait has children with a man who does not have the trait. What proportion of their daughters are expected to express the trait?

Accepted Answer

$$0.5$$

Cell Division and Chromosome Heredity: Mitosis, Meiosis, and Chromosomal Basis of Heredity

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