Question 1

Which of the following best describes the main difference between cytokinesis in animal cells and plant cells?

Accepted Answer

Animal cells use an actin-myosin ring to pinch the cell in two, while plant cells form a cell plate from vesicles directed by microtubules.

Question 2

A cell is observed to have chromosomes aligned at the center of the cell, each consisting of two sister chromatids. Which phase of mitosis is this cell most likely in?

Accepted Answer

Metaphase

Question 3

A mutation causes the $$G_1$$ checkpoint to fail in a group of cells. Which of the following is the most likely consequence?

Accepted Answer

Cells may divide uncontrollably, potentially leading to tumor formation.

Question 4

During DNA replication, which enzyme is responsible for relieving the twisting forces ahead of the replication fork?

Accepted Answer

Topoisomerase

Question 5

A scientist observes a cell with two nuclei, each containing the same number of chromosomes as the original cell, but the cytoplasm has not yet divided. Which stage has just completed?

Accepted Answer

Telophase

Question 6

Which of the following best explains why meiosis results in genetic variation among offspring?

Accepted Answer

Crossing over during Prophase I, independent assortment during Metaphase I, and random fertilization all contribute to genetic variation.

Question 7

A diploid organism ($$2n = 8) $$undergoes meiosis. How many chromosomes will each gamete contain after meiosis is complete?

Accepted Answer

$$4$$

Question 8

Which of the following statements about DNA replication is correct?

Accepted Answer

DNA replication is semi-conservative, producing two molecules each with one old and one new strand.

Question 9

A child is born with Down syndrome, which is caused by trisomy 21. Which meiotic error most likely led to this condition?

Accepted Answer

Nondisjunction during either Meiosis I or Meiosis II, resulting in an extra chromosome 21.

Question 10

In a dihybrid cross between two heterozygous pea plants ($$RrYy 	imes RrYy$$), what is the expected phenotypic ratio in the $$F_2$$ generation according to Mendel's principle of independent assortment?

Accepted Answer

$$9:3:3:1$$

Question 11

Which of the following best describes the role of DNA ligase during DNA replication?

Accepted Answer

It catalyzes the joining of Okazaki fragments on the lagging strand.

Question 12

A cell with a mutation in the gene encoding single-strand DNA-binding proteins (SSBPs) is likely to experience which problem during DNA replication?

Accepted Answer

The DNA strands will re-anneal after being separated, preventing replication.

Question 13

Which of the following scenarios best illustrates the principle of segregation?

Accepted Answer

A plant with genotype $$Aa$$ produces gametes, half carrying $$A$$ and half carrying $$a.$$

Question 14

A researcher is studying a gene located on the X chromosome. Which of the following inheritance patterns is most likely to be observed for a recessive allele of this gene?

Accepted Answer

It will affect males more frequently than females.

Question 15

Which of the following is an example of pleiotropy?

Accepted Answer

A single gene affects both fur color and eye color in mice.

Question 16

Which of the following best explains why the leading and lagging strands are synthesized differently during DNA replication?

Accepted Answer

DNA polymerase can only add nucleotides to the $$3'$$ end, so the lagging strand must be synthesized in short fragments as the fork opens.

Question 17

A cell is observed to have twice the normal amount of DNA but has not yet begun mitosis. In which phase of the cell cycle is this cell most likely found?

Accepted Answer

$$G_2$$

Question 18

Which of the following is a direct result of independent assortment during meiosis?

Accepted Answer

Each gamete receives a random mix of maternal and paternal chromosomes.

Question 19

A patient is diagnosed with a malignant tumor. Which of the following characteristics distinguishes this tumor from a benign tumor?

Accepted Answer

It is invasive and can metastasize to distant tissues.

Question 20

Which of the following best describes the relationship between the chromosome theory of inheritance and Mendel's principles?

Accepted Answer

The chromosome theory of inheritance explains that genes are located on chromosomes, which segregate and assort independently during meiosis, providing a physical basis for Mendel's principles.

Cell Cycle, Meiosis, DNA Replication, and Mendelian Genetics: Study Guide

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