Unknown Story
Текст Раскадровки
- 1. The first stage in meiosis I, is Prophase I. In this stage chromatin condense to form chromosomes, which are given their shape by a protein called histone. Pairs of replicated chromatids, also called sister chromatids, remain joined together at the centromere. The chromosomes migrate to the middle of the cell and the nuclear envelope disappears. In between this stage and the next, something called crossing-over occurs. This is when homologous chromosomes swap parts of themselves with the same genes and this phenomena is responsible for the law of Independent assortment.2. The second stage is metaphase I. In this stage, chromosomes line up on the metaphase plate with their homologous pair. The homologous chromosomes containing different alleles line up in this stage to be separated.3. The third stage is anaphase I, where the chromosomes are pulled to centrioles on opposite sides of the cell.4. The last stage is telophase, where the chromosomes are now completely pulled apart and nuclear envelopes form. The plasma membrane is separated by cytokinesis and two new cells are formed.Post-Meiosis I, two new haploid cells are formed. They are called haploid cells because they have two alleles for each gene but they are on sister chromatid copies of each other in DNA.
- Haploid Cell #1
- Haploid Cell #2
- 1. Meiosis II begins with prophase II, in which the nuclear envelope disappears and the centrioles are formed. Microtubules connect to individual chromatids.2. Next is metaphase II, where chromosomes line up along the metaphase plate. 3. Following metaphase II is Anaphase II. In this stage, sister chromatids separate and become sister chromosomes which are then pulled towards the centrioles. *Note* This is the final division of DNA in cell division.4. Lastly, is Telophase II. Now the chromosomes are on opposite sides of the cell and it is divided into two. Cytokinesis occurs and new nuclear envelopes are formed around the chromosomes. Post-Meiosis II, there are 4 haploid cells that each contain one copy of the genome. The cells can now be turned into gametes. Spermatogenesis is where the cells are developed into sperm cells in male reproductive organs. Oogenesis is where the cells turn into eggs in the female reproductive system.
- "Did all of that make sense?""...not at all"
- "Oh yeah! I almost forgot to mention polar bodies, the result of an oocyte meiotic division"
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