Q: Which of the following equations correctly represents the chromosome number changes during fertilization and meiosis in humans?

$$2n \xrightarrow{\text{meiosis}} n;\ n + n \xrightarrow{\text{fertilization}} 2n$$

Question 1

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

Accepted Answer

Chromatin refers to DNA wrapped around proteins during interphase, while chromosomes are the highly condensed structures visible during cell division.

Question 2

A scientist observes a cell with chromosomes aligned at the center of the cell, attached to spindle fibers from opposite poles. Which stage of mitosis is being observed?

Accepted Answer

Metaphase

Question 3

Which of the following statements about the cell cycle is correct?

Accepted Answer

G1, S, and G2 phases together make up interphase, during which the cell grows and replicates its DNA.

Question 4

A mutation causes a cell to ignore the G1 checkpoint. Which of the following is a likely consequence?

Accepted Answer

The cell may divide uncontrollably, potentially leading to cancer.

Question 5

Which of the following best explains why meiosis is essential for sexual reproduction in humans?

Accepted Answer

Meiosis reduces the chromosome number by half, so that fertilization restores the diploid number.

Question 6

During which stage of meiosis does crossing over occur, and what is its significance?

Accepted Answer

Crossing over occurs during prophase I, resulting in genetic recombination and increased genetic diversity.

Question 7

A karyotype of a human cell shows 47 chromosomes, including three copies of chromosome 21. Which term best describes this condition?

Accepted Answer

Trisomy

Question 8

Which of the following equations correctly represents the chromosome number changes during fertilization and meiosis in humans?

Accepted Answer

$$2n \xrightarrow{	ext{meiosis}} n;\ n + n \xrightarrow{	ext{fertilization}} 2n$$

Question 9

Which of the following mechanisms does NOT contribute to genetic variation in sexually reproducing organisms?

Accepted Answer

Binary fission in prokaryotes

Question 10

A researcher is studying a population of cells and finds that some cells have entered a non-dividing state. What is the name of this phase, and what is its significance?

Accepted Answer

G0 phase; cells have exited the cell cycle and are not actively dividing

Question 11

Which of the following best describes the role of cyclin-dependent kinases (Cdks) and cyclins in the cell cycle?

Accepted Answer

Cdks, when activated by binding to cyclins, phosphorylate target proteins to regulate progression through the cell cycle.

Question 12

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

Accepted Answer

Malignant tumors can invade surrounding tissues and metastasize to distant sites.

Question 13

Which of the following scenarios best illustrates density-dependent inhibition in cell division?

Accepted Answer

Cells stop dividing when they become crowded and touch neighboring cells.

Question 14

During which phase of mitosis do sister chromatids separate and move toward opposite poles of the cell?

Accepted Answer

Anaphase

Question 15

A cell with a diploid number of 8 ($$2n = 8) $$undergoes meiosis. How many chromosomes will each gamete contain after meiosis is complete?

Accepted Answer

$$4$$

Question 16

Which of the following events occurs during cytokinesis in animal cells?

Accepted Answer

Formation of a cleavage furrow that pinches the cell into two

Question 17

A geneticist observes a chromosome with a segment that has been reversed end to end. Which chromosomal mutation does this represent?

Accepted Answer

Inversion

Question 18

Which of the following best explains why cancer cells can continue to divide even when crowded and unattached to a substrate?

Accepted Answer

They have lost both density-dependent inhibition and anchorage dependence.

Question 19

Which of the following is a direct result of nondisjunction during meiosis?

Accepted Answer

Production of gametes with abnormal numbers of chromosomes (aneuploidy)

Question 20

A cell is observed to have a cell plate forming at its center during division. What type of cell is this, and what process is occurring?

Accepted Answer

Plant cell undergoing cytokinesis

Cell Division: The Cell Cycle, Mitosis, and Meiosis

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