Question 1

Which of the following best describes the difference between chromatin and chromosomes in eukaryotic cells?

Accepted Answer

Chromatin refers to DNA and associated proteins in a less condensed state during interphase, while chromosomes are highly condensed structures visible during cell division.

Question 2

A human somatic cell contains 46 chromosomes. After DNA replication but before mitosis, how many sister chromatids are present in the cell?

Accepted Answer

$$92$$

Question 3

Which of the following events distinguishes anaphase from metaphase during mitosis?

Accepted Answer

Sister chromatids are separated and pulled toward opposite poles.

Question 4

In a laboratory experiment, a researcher fuses a cell in S phase with a cell in G0 phase. What is the most likely outcome?

Accepted Answer

The G0 nucleus will be induced to begin DNA synthesis.

Question 5

Which of the following statements about the mitotic spindle is correct?

Accepted Answer

It is composed of microtubules and is essential for the segregation of sister chromatids.

Question 6

Which checkpoint in the cell cycle ensures that all chromosomes are properly attached to the spindle before sister chromatids separate?

Accepted Answer

M phase (spindle assembly) checkpoint

Question 7

How does cytokinesis differ between animal and plant cells?

Accepted Answer

Animal cells form a cleavage furrow, while plant cells build a cell plate from vesicles.

Question 8

Which of the following best explains why fission yeast was an excellent experimental system for identifying cell cycle regulators?

Accepted Answer

Fission yeast has a simple, easily manipulated genome and a cell cycle similar to that of higher eukaryotes.

Question 9

A cancer cell line is observed to grow even when densely packed and in suspension (not attached to a surface). Which cell cycle regulatory mechanisms are most likely defective in these cells?

Accepted Answer

Density-dependent inhibition and anchorage-dependent inhibition

Question 10

Which of the following is a key difference between mitosis and binary fission?

Accepted Answer

Mitosis involves the breakdown and reformation of the nuclear envelope, while binary fission does not.

Question 11

If a human gamete contains $$n$$ chromosomes, what is the value of $$n$$ and how many homologous pairs are present in a somatic cell?

Accepted Answer

$$n = 23$$; 23 homologous pairs

Question 12

Which enzyme is activated at the M phase checkpoint to allow the separation of sister chromatids?

Accepted Answer

Separase

Question 13

A researcher observes that a cell line continues to divide even after sustaining DNA damage and bypasses the G1 checkpoint. Which protein is most likely mutated or nonfunctional in these cells?

Accepted Answer

p53 tumor suppressor protein

Question 14

Which of the following best defines transformation in the context of cell culture?

Accepted Answer

The process by which a normal cell acquires the ability to divide indefinitely, often leading to cancer.

Question 15

Which of the following is a characteristic of a malignant tumor but not a benign tumor?

Accepted Answer

Cells can invade surrounding tissues and metastasize to distant sites.

Question 16

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

Accepted Answer

They are external signals that stimulate cells to divide by binding to specific receptors.

Question 17

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

Accepted Answer

S phase

Question 18

Which of the following best explains why cancer therapies often target rapidly dividing cells?

Accepted Answer

Cancer cells divide uncontrollably, so targeting cell division can limit tumor growth.

Question 19

Which of the following is true regarding homologous chromosomes in human somatic cells?

Accepted Answer

They carry the same genes but may have different alleles.

Question 20

A scientist observes a unicellular eukaryote with a cell division process that includes some features of both binary fission and mitosis. What does this observation suggest about the evolution of mitosis?

Accepted Answer

Mitosis likely evolved from simpler mechanisms such as binary fission, with intermediate forms present in some unicellular eukaryotes.

The Cell Cycle: Structure, Regulation, and Implications for Health

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