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 complex of cyclin and cyclin-dependent kinase (cdk) that triggers the cell's entry into mitosis by phosphorylating target proteins.

Question 2

A cell is observed to have membrane blebbing, DNA fragmentation, and formation of apoptotic bodies. Which process is most likely occurring, and what is a possible reason for this?

Accepted Answer

Apoptosis; the cell may have irreparable DNA damage.

Question 3

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

Accepted Answer

Prophase I; it increases genetic variation by exchanging genetic material between homologous chromosomes.

Question 4

A human cell with 46 chromosomes undergoes DNA replication. How many chromatids are present in the cell immediately after S phase?

Accepted Answer

$$92$$

Question 5

Which of the following best explains why cancer is considered a multi-hit disease?

Accepted Answer

Multiple mutations in genes regulating the cell cycle, such as proto-oncogenes and tumor suppressor genes, are typically required for cancer to develop.

Question 6

In Mendel’s dihybrid cross between two heterozygotes (AaBb x AaBb), what is the expected phenotypic ratio in the offspring?

Accepted Answer

$$9:3:3:1$$

Question 7

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

Accepted Answer

Autosomal dominant

Question 8

Which of the following scenarios best illustrates incomplete dominance?

Accepted Answer

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

Question 9

If a cell fails to pass the G1 checkpoint due to DNA damage, what are two possible fates for this cell?

Accepted Answer

The cell may undergo apoptosis or enter a non-dividing state (G0).

Question 10

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

Accepted Answer

Homologous chromosomes are similar but not identical chromosomes inherited from each parent, while sister chromatids are identical copies formed after DNA replication.

Question 11

A testcross is performed between a plant with an unknown genotype and a homozygous recessive plant. If all offspring display the dominant phenotype, what is the genotype of the unknown parent?

Accepted Answer

Homozygous dominant

Question 12

Which of the following events occurs during anaphase of mitosis?

Accepted Answer

Sister chromatids are separated and pulled toward opposite poles.

Question 13

Which process is responsible for the independent assortment of genes located on different chromosomes?

Accepted Answer

Random alignment of homologous chromosomes during metaphase I of meiosis.

Question 14

A mutation in a tumor suppressor gene is most likely to result in which of the following?

Accepted Answer

Loss of cell cycle control, increasing the risk of cancer.

Question 15

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, not its frequency; a dominant allele can be rare if it does not confer a selective advantage.

Question 16

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 17

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

Accepted Answer

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

Question 18

A woman who is a carrier for an X-linked recessive trait and a man who does not have the trait have a son. What is the probability that their son will express the trait?

Accepted Answer

$$0.5$$

Question 19

Which of the following is an example of a pleiotropic gene effect?

Accepted Answer

A single gene mutation causes multiple symptoms, such as in sickle cell disease affecting blood cells, pain, and organ function.

Cell Division, Genetics, and Regulation: Study Guide for Biology 161

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