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Answer:
prophase 1(Homologous chromosomes pair to form a tetrad.
prophase 1(Crossing-over may occur between the non-sister chromatids).
Metaphase 1 (Homologous chromosomes line up at the center of the cell.)
Anaphase 1 (Homologous pairs separate and move towards opposite ends of the cell)
Telophase 1 (A nuclear membrane forms and cytokinesis follows).
Metaphase 2 ( The haploid number of duplicated chromosomes line up at the metaphase plate.
Anaphase 2 (Sister chromatids separate and become daughter chromosomes that move to the poles)
Meiosis 2: Four haploid daughter cells are formed that are not genetically identical.
Explanation:
Meiosis is a type of cell division that gives rise to gametes ( offsprings). This type of cell division occurs only in the reproductive organs. A diploid cell has two sets of chromosomes: one from the female parent and the other one from the male parent. When the diploid cell undergoes meiosis, the chromosome replicate once and the nucleus and cell duplicate twice giving rise to four haploid gamete cells.
The phases of meiosis occurs in two step divisions. Homologous pairs separate during the first round cell division which occurs in MEIOSIS 1 while the sister chromatids separate in the second nuclear division called MEIOSIS 2.
In each round of division, cells go through four stages: PROPHASE, METAPHASE, ANAPHASE, and TELOPHASE. The specific events that occur in these stages are already listed in the above answer.
Generally, at the start of meiosis, each member of a homologous pair of chromosomes, which are made up of two chromatids, moves to lie side by side. While they are thus paired, genetic material is exchanged between the chromatids. This is known as CROSSING OVER.
When the nucleus divides for the first time, the chromosomes in a given pair( not the chromatids) separate and move to opposite ends of the cell. This results in only half the number of chromosomes going to each daughter cell.
During the second nuclear division, the chromatids separate and move to opposite ends of each daughter cell giving rise to four gamete cells, each with a haploid number of chromosomes.
Meiosis is the process through which haploid gametes are formed from a diploid germ cell. It takes place in two phases of four steps each: prophase, metaphase, anaphase and telophase.
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Through Meiosis, a diploid cell (2n) produces four haploid daughter cells (n).
After DNA replication there are two meiotic phases.
The first one is a reductive phase, in which homologous chromosomes separate.
In the second phase, the cell suffers a new, not reductive division.
1. In the first phase, Meiosis I:
- Prophase I: Chromosomes condensate and become visible. Occurs crossing-over between homologous chromosomes. Crossin-over makes the daughter cells to be genetically different from the original one.
- Metaphase I: Homologous chromosomes randomly align in the equatorial plane.
- Anaphase I: In this phase occurs the division and independent separation of homologous pairs. Each chromosome migrates to different poles. This separation generates different chromosomal combinations in the daughter cells.
- Telophase I: Chromosomes of homologous pairs are already in the corresponding poles, and the nuclear membrane forms again in each pole.
2. In the second phase, Meiosis II:
- Prophase II: Chromosomes condensate again and become visible.
- Metaphase II: Chromosomes join the spindle apparatus and migrate to the equatorial plane, where they randomly line up. Sister chromatids are holden together until they reach the Anaphase.
- Anaphase II: Centromeres divide, chromatids get separated, and each of them goes forward an opposite cellular pole.
- Telophase II: Once in the poles, the chromosomes become lax again, and the nuclear membrane forms again.
Cytokinesis occurs at the end of Meiosis II. The final products are four haploid cells different from the original one.
According to this information, the correct order would be as follows
- Prophase 1: Homologous chromosomes pair to form a tetrad.
- Prophase 1: Crossing-over may occur between the non-sister chromatids.
- Metaphase 1: Homologous chromosomes line up at the center of the cell.
- Anaphase 1: Homologous pairs separate and move towards opposite ends of the cell.
- Telophase 1: A nuclear membrane forms and cytokinesis follows.
- Metaphase 2: The haploid number of duplicated chromosomes line up at the metaphase plate.
- Anaphase 2: Sister chromatids separate and become daughter chromosomes that move to the poles.
- Meiosis 2: Four haploid daughter cells are formed that are not genetically identical.
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