Question 1

Which of the following best explains why cancer can result from the loss of cell cycle checkpoint control?

Accepted Answer

Cells begin to divide uncontrollably, potentially accumulating mutations and forming malignant tumors.

Question 2

During which phase of the cell cycle is DNA replicated, and what is the result of this replication?

Accepted Answer

S phase; each chromosome consists of two sister chromatids joined at the centromere.

Question 3

A researcher observes a cell with a circular DNA molecule and small, extra-chromosomal DNA pieces. Which type of cell is being observed, and what are the extra-chromosomal pieces called?

Accepted Answer

Prokaryotic cell; plasmids

Question 4

Which of the following events occurs during prophase of mitosis?

Accepted Answer

Chromatin condenses into visible chromosomes and the mitotic spindle begins to form.

Question 5

In plant cells, cytokinesis differs from animal cells because:

Accepted Answer

A cell plate forms from vesicles that fuse at the center of the cell.

Question 6

Which of the following best describes the Law of Independent Assortment?

Accepted Answer

Alleles of different genes are distributed to gametes independently of one another during meiosis.

Question 7

A woman who is heterozygous for a recessive genetic disorder and a man who is homozygous dominant have a child. What is the probability that their child will be a carrier?

Accepted Answer

$$\frac{1}{2}$$

Question 8

Which of the following is an example of pleiotropy?

Accepted Answer

A single gene causing both sickle-shaped red blood cells and resistance to malaria.

Question 9

During meiosis, which event is responsible for increasing genetic diversity by exchanging genetic material between homologous chromosomes?

Accepted Answer

Crossing over during prophase I

Question 10

A male inherits a recessive X-linked disorder from his mother. Which of the following explains why X-linked diseases are more common in males than females?

Accepted Answer

Males have only one X chromosome, so a single recessive allele will result in the disorder.

Question 11

Which of the following best describes the structure of DNA?

Accepted Answer

A double helix with two antiparallel strands, a sugar-phosphate backbone joined by covalent phosphodiester bonds, and complementary bases paired by hydrogen bonds.

Question 12

Which enzyme is responsible for joining Okazaki fragments on the lagging strand during DNA replication?

Accepted Answer

DNA ligase

Question 13

A cell with 2n = 8 undergoes meiosis. How many chromosomes will each gamete contain after meiosis is complete?

Accepted Answer

4

Question 14

A geneticist performs a testcross between a pea plant with an unknown genotype for a dominant trait and a homozygous recessive plant. What is the purpose of this testcross?

Accepted Answer

To determine whether the unknown plant is homozygous dominant or heterozygous for the trait.

Question 15

Which of the following chromosomal abnormalities results from the failure of homologous chromosomes to separate during meiosis?

Accepted Answer

Nondisjunction

Question 16

A child is born with Trisomy 21. Which of the following best explains the genetic cause of this condition?

Accepted Answer

The child has three copies of chromosome 21 due to nondisjunction during meiosis.

Question 17

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

Accepted Answer

Homologous chromosomes are similar but not identical, each inherited from a different parent; sister chromatids are identical copies of a single chromosome.

Question 18

In a dihybrid cross between two heterozygous individuals (AaBb x AaBb), what is the expected phenotypic ratio in the F2 generation, assuming independent assortment?

Accepted Answer

$$9:3:3:1$$

Question 19

Which scientist(s) used X-ray diffraction to help determine the structure of DNA?

Accepted Answer

Rosalind Franklin and Maurice Wilkins

Question 20

A geneticist calculates a recombination frequency of 12% between two genes. What does this indicate about the genes' locations?

Accepted Answer

The genes are relatively close together on the same chromosome.

Cell Division, Inheritance, and the Molecular Basis of Genetics

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