Question 1

Which phase of the cell cycle is primarily responsible for DNA replication, and what is the main event that occurs during this phase?

Accepted Answer

S phase; DNA is duplicated

Question 2

During which phase of the cell cycle does the cell spend the majority of its time, and what is the primary activity during this phase?

Accepted Answer

Interphase; cell growth and DNA replication

Question 3

A neuron in an adult human is most likely to be found in which phase of the cell cycle?

Accepted Answer

G0 phase

Question 4

Which of the following best describes the structure of DNA in the nucleus during interphase?

Accepted Answer

Long, thin strands of chromatin

Question 5

What is the role of histone proteins in the organization of DNA?

Accepted Answer

They act as spools for DNA to wind around, compacting it

Question 6

If a human cell has just completed S phase, how many chromosomes are present in the nucleus?

Accepted Answer

46 chromosomes, each with two sister chromatids

Question 7

Which of the following equations correctly represents the number of base pairs in the human genome?

Accepted Answer

$$3 	imes 10^9$

Question 8

A mutation occurs in a gene located on chromosome 7. What is the best definition of a gene in this context?

Accepted Answer

A segment of DNA that codes for one or more proteins

Question 9

Which phase of the cell cycle immediately precedes mitosis, and what is the cell primarily doing during this phase?

Accepted Answer

G2 phase; cell prepares for division

Question 10

During which stage of the cell cycle are chromosomes most visible under a microscope, and why?

Accepted Answer

Mitotic phase; chromosomes condense

Question 11

Which of the following best explains why neurons and osteocytes remain in the G0 phase after adolescence?

Accepted Answer

They are specialized cells that do not divide

Question 12

A scientist observes a cell with visible sister chromatids held together by a centromere. Which phase is this cell most likely in?

Accepted Answer

Mitotic phase

Question 13

Which of the following statements about chromosomes is correct?

Accepted Answer

Humans have 46 chromosomes organized into 23 pairs

Question 14

If a cell cycle takes 24 hours and the S phase lasts 8 hours, what fraction of the cell cycle is spent in S phase? Express your answer as a simplified fraction.

Accepted Answer

$$\frac{1}{3}$$

Question 15

Which process ensures that each new cell receives an exact copy of the parental DNA during cell division?

Accepted Answer

DNA replication during S phase

Question 16

A cell is observed to be growing rapidly and synthesizing proteins, but not yet duplicating its DNA. Which phase is it in?

Accepted Answer

G1 phase

Question 17

Which of the following best describes cytokinesis?

Accepted Answer

Division of the cytoplasm

Question 18

If a mutation prevents a cell from entering G2 phase, which process will be directly affected?

Accepted Answer

Preparation for mitosis

Question 19

Which of the following is a correct sequence of events in the cell cycle?

Accepted Answer

G1 → S → G2 → Mitosis → Cytokinesis

Question 20

Which of the following best explains why DNA must be duplicated before mitosis?

Accepted Answer

To ensure each daughter cell receives a full set of genetic material

Cell Cycle and DNA Structure: Study Notes for Human Biology

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