Question 1

During which phase of the cell cycle does DNA replication occur, and what is the significance of this process for cell division?

Accepted Answer

DNA replication occurs during the S phase, allowing each daughter cell to receive an identical set of chromosomes.

Question 2

A mutation occurs in a somatic cell during DNA replication. Which of the following best describes the potential consequences of this mutation?

Accepted Answer

The mutation may affect the function of the tissue or cause cancer, but will not be inherited by offspring.

Question 3

Which of the following best explains why humans can produce more proteins than the number of genes present in the genome?

Accepted Answer

Alternate splicing and alternate reading frames allow a single gene to produce multiple proteins.

Question 4

Which of the following events occurs during prophase of mitosis?

Accepted Answer

Chromatin condenses into visible chromosomes and the nuclear membrane dissolves.

Question 5

A researcher observes a cell with chromosomes aligned in a single line at the equator of the cell. Which stage of mitosis is being observed?

Accepted Answer

Metaphase

Question 6

Which of the following statements about meiosis is correct?

Accepted Answer

Meiosis reduces the chromosome number by half, resulting in four non-identical haploid cells.

Question 7

Crossing over, which increases genetic diversity, occurs during which specific stage of meiosis?

Accepted Answer

Prophase I

Question 8

A cell is observed to have just completed cytokinesis, resulting in two daughter cells. Which of the following best describes the genetic content of these cells if the process was mitosis?

Accepted Answer

Each daughter cell is diploid and genetically identical to the parent cell.

Question 9

Which of the following best describes the role of tRNA during translation?

Accepted Answer

tRNA brings specific amino acids to the ribosome by matching its anticodon to the mRNA codon.

Question 10

A mutation in a gene coding for a DNA repair enzyme increases the risk of cancer. Why?

Accepted Answer

DNA repair enzymes are responsible for correcting errors in DNA; without them, mutations accumulate, potentially leading to cancer.

Question 11

Which of the following is true regarding the start and stop codons in the genetic code?

Accepted Answer

AUG is the start codon, and UAA, UAG, and UGA are stop codons.

Question 12

A scientist is attempting to clone a sheep using somatic cell nuclear transfer. Which of the following best describes the genetic relationship between the clone and the original sheep?

Accepted Answer

The clone is genetically identical to the sheep that provided the somatic cell.

Question 13

Which checkpoint in the cell cycle ensures that DNA has been properly replicated before the cell enters mitosis?

Accepted Answer

$$G_2$$ checkpoint

Question 14

Why is differentiation important in multicellular organisms?

Accepted Answer

It enables cells to become specialized for specific functions, allowing complex tissues and organs to form.

Question 15

A zygote divides several times without growing, forming a ball of cells. At which stage is embryo splitting (for cloning) possible, and why does this become impossible later?

Accepted Answer

Embryo splitting is possible at the 8-cell stage because cells are not yet differentiated; after the 16-cell stage, differentiation begins and splitting is no longer effective.

Question 16

Which of the following best describes the difference in gamete production between males and females during meiosis?

Accepted Answer

Males produce four sperm; females produce one egg and three polar bodies.

Question 17

A patient is exposed to a mutagen during early fetal development. Which of the following is the most likely outcome?

Accepted Answer

The embryo or fetus may not survive due to the vulnerability of early development.

Question 18

Which of the following best describes the process of transcription?

Accepted Answer

Transcription is the process of copying DNA into mRNA within the nucleus.

Question 19

A cell is observed to have 23 pairs of chromosomes, including one pair of sex chromosomes (XX). Which of the following best describes this cell?

Accepted Answer

It is a diploid somatic cell from a female.

Cell Reproduction and Differentiation: The Cell Cycle, DNA Structure, and Genetic Mechanisms

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