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In reality, crossing-over between chromatids during prophase I of meiosis mixes up pieces of chromosomes between homologue pairs, a phenomenon called recombination.
- Walther Flemming
The German anatomist Walther Flemming began his pioneering...
- Walther Flemming
Dec 15, 2022 · In the cells of our body, we start with 46 chromosomes in a single cell and end up with 46 chromosomes in two cells. Obviously, replicating the chromosomes is a prerequisite to mitosis. Remember, replication takes place during interphase when the chromosomes are dispersed structures in the nucleus.
Notice that with two homologous pairs of chromosomes, we can create four unique combinations. That’s 2 2 . With three homologous pairs, there are 8 possibilities, which is 2 3 .
During meiosis in humans, 1 diploid cell (with 46 chromosomes or 23 pairs) undergoes 2 cycles of cell division but only 1 round of DNA replication. The result is 4 haploid daughter cells known as gametes or egg and sperm cells (each with 23 chromosomes – 1 from each pair in the diploid cell).
- Steps of Meiosis I
- Result of Meiosis I
- What Is The End Result of Meiosis
1) Prophase I
It is the longest phase of meiotic division involving a series of events and is divided into the following steps: 1. The duplicated chromosomes condense, resembling an X-shaped structure with two sister chromatids that become distinctly visible within the nucleus. 2. The homologous chromosome pair (one inherited from each parent) comes closer and associate along the entire chromosome length, forming a tetrad. Each tetrad is composed of four chromatids. 3. The homologous chromosomes exchange p...
2) Metaphase I
1. Homologous chromosomes align along the center of the cell. 2. The centrioles reach the opposite poles of the cell with the spindle fibers extending from them. 3. The centromeres orient themselves towards the opposite poles of the cell.
3) Anaphase I
1. The chromosomes with two sister chromatids are separated, and they begin to migrate to the opposite poles. This separation is achieved because of the contraction of the spindle fibers attached to each chromosome’s centromere. 2. The homologous chromosomes start to migrate to the opposite poles.
At the end of cytokinesis I, two different daughter cells are formed, each with half the number of chromosomes as the parent cell(having 23 chromosomes having 23 pairs of chromatids). Meiosis is thus also called the reduction division.
Thus at the end of meiosis II,four non-identical, haploid daughter cells are formed, each having half chromosome number as the original parent cell.
If those two cells each contain one set of chromosomes, then the resulting cell contains two sets of chromosomes. Haploid cells contain one set of chromosomes, diploid cells contain two sets of chromosomes. The number of sets of chromosomes in a cell is called its ploidy level.
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Oct 21, 2023 · Steps of Meiosis. Meiosis is a type of cell division that reduces the chromosome number by half (2n to n), leading to the formation of four non-identical daughter cells. It is crucial for sexual reproduction in eukaryotes. Meiosis involves two divisions, so it’s typically broken down into meiosis I and meiosis II.
