Question 1

Which of the following best explains why sexual reproduction leads to greater genetic variation in offspring compared to asexual reproduction?

Accepted Answer

Sexual reproduction combines gametes from two parents and includes processes such as crossing over and independent assortment.

Question 2

During which phase of the cell cycle is DNA replicated?

Accepted Answer

S phase

Question 3

A researcher observes a cell with chromosomes aligned at the metaphase plate, spindle fibers attached, and the nuclear envelope completely dissolved. Which stage of mitosis is this cell in?

Accepted Answer

Metaphase

Question 4

Which checkpoint in the cell cycle is primarily responsible for ensuring that all chromosomes are properly attached to the spindle before the cell proceeds with division?

Accepted Answer

M checkpoint

Question 5

A patient is treated with methotrexate, a drug that blocks the synthesis of thymine. What is the most direct effect of this drug on cancer cells?

Accepted Answer

It blocks DNA replication, preventing cell division.

Question 6

Which of the following events occurs during prophase I of meiosis but NOT during prophase of mitosis?

Accepted Answer

Homologous chromosomes pair up and crossing over occurs.

Question 7

If a human cell with 46 chromosomes undergoes meiosis, how many chromosomes will each resulting gamete contain?

Accepted Answer

$$23$$

Question 8

A cell is observed to be dividing uncontrollably and does not respond to density-dependent inhibition or anchorage dependence. What is the most likely diagnosis?

Accepted Answer

The cell is cancerous.

Question 9

Which chromosomal abnormality results from a failure of homologous chromosomes to separate during meiosis I?

Accepted Answer

Nondisjunction

Question 10

A karyotype of a human cell shows 47 chromosomes, including three copies of chromosome 21. What is the diagnosis?

Accepted Answer

Down syndrome (Trisomy 21)

Question 11

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

Accepted Answer

Chromatin is loose, uncondensed DNA present when the cell is not dividing; chromosomes are tightly packed DNA visible during cell division.

Question 12

Which process is responsible for the random distribution of maternal and paternal chromosomes to gametes during meiosis?

Accepted Answer

Independent assortment

Question 13

A mutation causes a segment of a chromosome to break off, flip, and reattach in the reverse orientation. What is this type of chromosomal alteration called?

Accepted Answer

Inversion

Question 14

Which of the following is a direct result of the failure of the spindle assembly checkpoint during mitosis?

Accepted Answer

Chromosomes may not be properly separated, leading to aneuploidy.

Question 15

A plant cell is undergoing cytokinesis. What structure forms to separate the two daughter cells?

Accepted Answer

Cell plate

Question 16

If $$n = 3$$ for a species, how many possible combinations of chromosomes can result from independent assortment alone (ignoring crossing over and fertilization)?

Accepted Answer

$$2^3 = 8$

Question 17

Which of the following best explains why individuals with Turner syndrome (XO) can survive, while most other monosomies are lethal?

Accepted Answer

The X chromosome undergoes inactivation, so one X is sufficient for survival.

Question 18

Which of the following is NOT a source of genetic variation in sexually reproducing organisms?

Accepted Answer

Replication of DNA during S phase

Question 19

A cancerous tumor that invades surrounding tissues and can spread to other parts of the body through blood or lymph is called:

Accepted Answer

Malignant tumor

Question 20

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.

Cell Division, Cell Cycle, Mitosis, Meiosis, and Chromosomal Disorders: Study Guide

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