1) Which of the statements below is NOT TRUE about meiosis and/or mitosis.

A) One reason meiosis I is different from mitosis because homologous pairs of chromosomes line up next to each other and then separate.

B) Daughter cells are produced in meiosis with half the number of chromosomes as the parent cell.

C) No exchange of genetic material is exchanged during meiosis, so there is no genetic diversity as a result of this process.

6) Which of the following is a TRUE statement about crossing over?

A) Crossing over occurs in both mitosis and meiosis I

B) Crossing over occurs during prophase I of meiosis; because of crossing over, genetic variation in the resulting gametes is increased.

C) Crossing over occurs in telophase II of meiosis; it decreases the genetic variability in the gametes produced.

Meiosis is a type of cell division which results in the production of four daughter cells from a single parent cell. Each daughter cell contains half the chromosomes present in the parent cell.

In addition, the event of crossing over also takes place during prophase I of meiosis I. It results in the exchange of genetic material between non-sister chromatids of homologous chromosomes.

6) The correct answer would be option B.

Crossing over is the event that takes place during prophase I especially during the pachytene stage. The exchange of genetic material between non-sister chromatids of homologous chromosomes takes place during crossing over. It helps in increasing genetic diversity among the population.

avantikar avantikar · Answer 2 · 2020-03-07T10:04:40+01:00

1. Crossing over occurs during meiosis, which results in the exchange of genetic material. This leads to the formation of genetically diverse gametes at the end of meiosis.

Further Explanation:

When a single cell undergoes division twice to produce four-cell, each containing half the number of chromosomes as the parent cell, the process is called meiosis. Meiosis occurs in germ cells such as eggs ad sperms in females and males, respectively. It is divided into two stages: meiosis I and meiosis II. Meiosis I involves interphase as the first stage during which DNA replication occurs. The next stage is prophase I, in which the chromosomes condense to form an X shaped structure. This structure contains two sister chromatids from each chromosome of the pair. The genetic information is exchanged between the pair of homologous chromosomes through crossing over or recombination. This is followed by metaphase I in which the homologous chromosomes align at the center. In the anaphase I, the homologous pair separates and moves in the opposite direction while keeping the sister chromatids intact. Cytokinesis occurs in the telophase I. In this phase; the parent cell pinches into two daughter cells that start meiosis II. It includes stages like prophase II, metaphase II, anaphase II, and telophase II. These stages lead to the formation of four haploid gametes. These gametes show genetic variation due to recombination.

The process of mitosis comprises the division of a single cell into two similar cells containing the same chromosome number as the original cell. Mitosis also involves similar stages, such as interphase, prophase, metaphase, anaphase, and telophase. But it does not include the exchange of genetic material during prophase. Therefore, at the end of mitosis, cells with similar genetic makeup are formed.

2. Prophase stage of meiosis I include crossing over because of which genetic variation increases in the gametes produced.

Further Explanation:

Crossing over is a process in which equal segments of chromosomes are transferred in the homologous pair. It takes place during meiosis in the prophase I stage. In this stage, the chromosomes have duplicated and the sister chromatids have formed. At a point, the two homologous chromosomes come together and form a synapse. During synapse, breakage occurs in one chromatid from each pair of the homologous chromosomes. The exchange of genes occurs at the broken segments to form a new combination of genes. This results in the formation of new gene pairs in the corresponding chromosome. When the sister chromatids separated in the meiosis II, gametes are formed in which some gametes contain newly formed genetic composition while some contain inherited genes. Therefore, crossing over enhances variation in genetic makeup.

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Answer Details:

Grade: Senior School

Chapter: Cell division

Subject: Biology

Keywords:

Meiosis, homologous chromosomes, DNA replication, interphase, metaphase, prophase, anaphase, telophase, sister chromatids, synapse, genetic material, genes, gametes, mitosis, crossing over, recombination.