Question 1

Which of the following best describes the role of maturation promoting factor (MPF) in the regulation of the cell cycle?

Accepted Answer

MPF is a protein complex composed of cyclin and cyclin-dependent kinase (cdk) that triggers the cell's entry into mitosis when activated.

Question 2

A cell is observed to have condensed chromosomes aligned at the center of the cell, with spindle fibers attached to the centromeres. Which phase of mitosis is this cell in?

Accepted Answer

Metaphase

Question 3

Which of the following events increases genetic variation during meiosis?

Accepted Answer

Crossing-over during prophase I and independent assortment during metaphase I

Question 4

A genetic cross between two heterozygous individuals for a single trait (Aa x Aa) results in which expected phenotypic ratio in the offspring?

Accepted Answer

$$3:1$$

Question 5

Which of the following best explains why dominant traits are not always the most common traits in a population?

Accepted Answer

Dominance refers to the expression of an allele in the heterozygote, not its frequency in the population.

Question 6

A pedigree shows that a trait appears in every generation and affects both males and females equally. Which inheritance pattern is most likely?

Accepted Answer

Autosomal dominant

Question 7

During which phase of the cell cycle does DNA replication occur?

Accepted Answer

S phase

Question 8

Which of the following scenarios is an example of incomplete dominance?

Accepted Answer

A cross between red-flowered and white-flowered snapdragons produces pink-flowered offspring.

Question 9

A human cell with 46 chromosomes undergoes meiosis. How many chromosomes will each resulting gamete contain?

Accepted Answer

$$23$$

Question 10

Which of the following best describes the process and significance of apoptosis?

Accepted Answer

Apoptosis is programmed cell death involving DNA fragmentation, membrane blebbing, and engulfment by macrophages, which prevents damage to neighboring cells.

Question 11

Which of the following is a key difference between oogenesis and spermatogenesis in humans?

Accepted Answer

Oogenesis produces one viable egg and polar bodies, while spermatogenesis produces four viable sperm.

Question 12

A cell fails to pass the G1 checkpoint due to DNA damage. Which of the following is a possible fate for this cell?

Accepted Answer

The cell may undergo apoptosis to prevent propagation of mutations.

Question 13

Which of the following best describes the difference between homologous chromosomes and sister chromatids?

Accepted Answer

Homologous chromosomes are pairs of chromosomes with the same genes but possibly different alleles, while sister chromatids are identical copies formed during DNA replication.

Question 14

Which of the following is a function of tumor suppressor genes in the cell cycle?

Accepted Answer

They halt the cell cycle at checkpoints to allow for DNA repair or trigger apoptosis if damage is irreparable.

Question 15

Which of the following best explains the multi-hit hypothesis in cancer development?

Accepted Answer

Multiple mutations in genes regulating the cell cycle are required for a normal cell to become cancerous.

Question 16

During which stage of meiosis does crossing-over occur, and what is its significance?

Accepted Answer

Crossing-over occurs during prophase I and increases genetic diversity by exchanging genetic material between homologous chromosomes.

Question 17

A woman with genotype $$X^N X^n ($$where $$N is $$normal and $$n is a $$recessive X-linked disorder) and a man with genotype $$X^n Y$$ have children. What is the probability that a son will have the disorder?

Accepted Answer

$$50\%$$

Question 18

A scientist adds cytoplasm from a dividing cell to a non-dividing cell, which then enters mitosis. What is the most likely explanation for this observation?

Accepted Answer

The cytoplasm contains active MPF (cyclin + cdk), which triggers mitosis in the recipient cell.

Question 19

Which of the following best describes the function of telomerase in eukaryotic cells?

Accepted Answer

Telomerase extends the telomeres at the ends of chromosomes, preventing their shortening during DNA replication.

Cell Division, Genetics, and Inheritance: Study Guide for Biology 161 Test 4

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