Question 1

Which of the following best describes the difference between euchromatin and heterochromatin in a human cell nucleus?

Accepted Answer

Euchromatin is less compacted and generally transcriptionally active, while heterochromatin is more compacted and generally transcriptionally inactive.

Question 2

During which phase of the cell cycle does DNA replication occur, and what is the ploidy of a human somatic cell immediately after this phase?

Accepted Answer

DNA replication occurs during S phase; the cell is diploid (2N) but with duplicated chromosomes.

Question 3

Which of the following equations correctly represents the number of chromatids in a human somatic cell during metaphase of mitosis?

Accepted Answer

$$46 \times 2 = 92$$

Question 4

A researcher observes a cell that continues to divide even when surrounded by other cells and without being attached to a surface. Which property of normal cells is most likely lost in this cell?

Accepted Answer

Density-dependent inhibition and anchorage dependence

Question 5

Which of the following best describes the role of the mitotic spindle during mitosis?

Accepted Answer

It organizes the chromosomes and separates sister chromatids by attaching to kinetochores.

Question 6

A mutation in the Ras gene leads to continuous cell division even in the absence of growth factors. What type of gene is Ras, and what is the consequence of its mutation?

Accepted Answer

Ras is a proto-oncogene; its mutation can convert it into an oncogene, promoting uncontrolled cell division.

Question 7

Which of the following is a function of the p53 protein in the cell cycle?

Accepted Answer

Inhibits the cell cycle, repairs damaged DNA, and can induce apoptosis.

Question 8

A tumor is found to be spreading through the bloodstream to other tissues. According to the multistep model of cancer, what type of tumor is this and what does this indicate about its genetic mutations?

Accepted Answer

Malignant tumor; it has accumulated multiple mutations in proto-oncogenes and tumor-suppressor genes.

Question 9

Which of the following best explains why skin cells are able to heal wounds quickly compared to neurons in the central nervous system?

Accepted Answer

Skin cells have a higher rate of cell turnover due to frequent cell division, while neurons rarely divide after development.

Question 10

Which of the following is true about the organization of DNA in the nucleus during interphase?

Accepted Answer

DNA is organized as chromatin, which is less condensed than mitotic chromosomes.

Question 11

Which of the following best describes the function of kinetochores during mitosis?

Accepted Answer

Kinetochores serve as attachment points for spindle microtubules, facilitating chromosome movement.

Question 12

A scientist observes a cell with a contractile ring of actin microfilaments forming a cleavage furrow. Which stage of the cell cycle is this cell most likely in?

Accepted Answer

Cytokinesis

Question 13

Which of the following equations correctly represents the relationship between the number of chromosomes ($$n) $$and the number of chromatids ($$c) in a $$human cell after DNA replication but before mitosis?

Accepted Answer

$$c = 2n$$

Question 14

Which of the following scenarios best illustrates the concept of density-dependent inhibition?

Accepted Answer

A single cell divides rapidly in a petri dish until it covers the entire surface, then stops dividing.

Question 15

Which of the following is a key difference between benign and malignant tumors?

Accepted Answer

Malignant tumors invade surrounding tissues and can metastasize, while benign tumors remain localized.

Question 16

Which of the following best describes the role of growth factors in the cell cycle?

Accepted Answer

Growth factors are external chemical signals that stimulate cell division.

Question 17

A patient is diagnosed with a tumor that has not spread to other tissues and is easily removed by surgery. According to the multistep model of cancer, what is the most likely classification of this tumor?

Accepted Answer

Benign tumor

Question 18

Which of the following best explains why mutations in both proto-oncogenes and tumor-suppressor genes are often required for cancer to develop?

Accepted Answer

Proto-oncogenes promote cell division, while tumor-suppressor genes inhibit it; mutations in both remove normal controls on the cell cycle.

LESSON 5 Cell Cycle and Tumor Formation: Structure, Regulation, and Cancer Development

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