Unit 2, week 3

How many gametes are produced by meiosis?

• 1

• 2

• 3

• 4

• 5

Answer explanation

Meiosis is a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell. This process is fundamental to sexual reproduction and leads to the formation of gametes. Therefore, the correct answer is that 4 gametes are produced by meiosis.

In which phase does crossing over occur?

• Anaphase I

• Anaphase II

• Prophase I

• Prophase II

• S phase

Answer explanation

Crossing over, a process in which genetic material is exchanged between homologous chromosomes, occurs during the prophase I stage of meiosis. This phase is marked by the pairing of homologous chromosomes and the potential for genetic recombination. The other options like Anaphase I, Anaphase II, Prophase II and S phase do not involve crossing over.

What is the name of the section of chromosome where crossing over occurs?

• Centromere

• Chromatid

• Chiasma

• Telomere

• Tetrad

Answer explanation

The correct answer is Chiasma. In the process of genetic recombination, chromosomes swap segments at points called 'chiasmata'. This occurs in the pachytene (P) stage of meiosis during the formation of sperm and egg cells. Other options like Centromere, Chromatid, Telomere and Tetrad do not refer to the section of a chromosome where crossing over occurs.

In which phase of meiosis does the nuclear membrane reform?

• Prophase I

• Metaphase II

• Anaphase I

• Telophase I

• None of the above

Answer explanation

In the Telophase I phase of meiosis, the nuclear membrane begins to reform around the separated sister chromatids. This is the point where a single cell splits into two cells, each with half the number of chromosomes as the original cell. This process is crucial in the production of sex cells for reproduction.

In meiosis, how many chromosomes are present during metaphase I?

• 46

• 23

• 92

• 4

• 12

Answer explanation

In meiosis, during metaphase I, each chromosome aligns with its homologous partner, forming a structure known as a bivalent or tetrad. As humans have 23 pairs of chromosomes, during metaphase I in meiosis, there are 46 chromosomes present. Therefore, the correct answer is 46.

During which phase of meiosis do homologous chromosomes separate?

• Prophase I

• Metaphase I

• Anaphase I

• Telophase I

• None of the above

Answer explanation

In the Anaphase I phase of meiosis, homologous chromosomes are separated. This is because the spindle fibers pull each homologous chromosome pair toward opposite ends of the cell. So, the correct choice is Anaphase I. The other options listed, Prophase I, Metaphase I, Telophase I, and None of the above, are not the phases during which this specific activity occurs.

What is the process of cell division that produces gametes called?

• Meiosis

• Mitosis

• Cytokinesis

• Interphase

• Prophase

Answer explanation

The process of cell division that produces gametes is called Meiosis. It's a special type of cell division in sexual reproduction which results in four daughter cells each with half the number of chromosomes of the parent cell. This is in contrast with Mitosis, which is used for growth and repair and results in identical cells. Cytokinesis, Interphase, and Prophase are stages of cell division, not specific to the production of gametes.

What is the structure that holds two sister chromatids together?

• Centromere

• Chiasma

• Telomere

• Tetrad

• Chromatid

Answer explanation

The structure that holds two sister chromatids together is called a centromere. It plays a vital role during cell division where the chromosomes divide. The other options such as chiasma, telomere, tetrad and chromatid do not serve this particular function.

What is the result of meiosis?

• 2 diploid cells

• 4 diploid cells

• 2 haploid cells

• 4 haploid cells

• 1 diploid cell

Answer explanation

Meiosis is a process of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell. These daughter cells are referred to as haploid cells, thus the result of meiosis is 4 haploid cells.

When does the separation of sister chromatids occur in meiosis?

• Anaphase I

• Anaphase II

• Prophase I

• Prophase II

• Metaphase I

Answer explanation

The separation of sister chromatids happens in Anaphase II during the meiosis process. Anaphase I is noted for the separation of homologous chromosomes, while in Prophase I and II, chromosomes condense and prepare for division. In Metaphase I, homologous chromosomes align at the equator. However, Anaphase II specifically deals with splitting of sister chromatids.