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A tetrad is a group of four chromatids formed from each of a pair of homologous chromosomes that split longitudinally during the prophase of meiosis. Tetrads are important in meiosis because they allow for the process of crossing over, where segments of non-sister chromatids can exchange genetic material. This results in new combinations of ...
Nov 21, 2023 · Learn what a tetrad in meiosis is, what chromosomes form tetrads, and when tetrad formation occurs. Understand the importance of tetrad in crossing over. Updated: 11/21/2023.
The tetrad is the four spores produced after meiosis of a yeast or other Ascomycota, Chlamydomonas or other alga, or a plant. After parent haploids mate, they produce diploids. Under appropriate environmental conditions, diploids sporulate and undergo meiosis.
At the end of prophase I, the pairs are held together only at the chiasmata (Figure 11.1.2 11.1. 2) and are called tetrads because the four sister chromatids of each pair of homologous chromosomes are now visible. The crossover events are the first source of genetic variation in the nuclei produced by meiosis.
- Prophase I. Early in prophase I, before the chromosomes can be seen clearly microscopically, the homologous chromosomes are attached at their tips to the nuclear envelope by proteins.
- Prometaphase I. The key event in prometaphase I is the attachment of the spindle fiber microtubules to the kinetochore proteins at the centromeres. Kinetochore proteins are multiprotein complexes that bind the centromeres of a chromosome to the microtubules of the mitotic spindle.
- Metaphase I. During metaphase I, the homologous chromosomes are arranged in the center of the cell with the kinetochores facing opposite poles. The homologous pairs orient themselves randomly at the equator.
- Anaphase I. In anaphase I, the microtubules pull the linked chromosomes apart. The sister chromatids remain tightly bound together at the centromere. The chiasmata are broken in anaphase I as the microtubules attached to the fused kinetochores pull the homologous chromosomes apart (Figure 4).
Oct 21, 2023 · Homologous chromosomes (chromosomes with the same genes but possibly different versions of those genes) come together in pairs in a process called synapsis, forming tetrads. Crossing-over, or genetic recombination, occurs, where sections of chromatids from one chromosome exchange places with sections from its homologous chromosome.
Oct 31, 2023 · At the end of prophase I, the pairs are held together only at the chiasmata; they are called tetrads because the four sister chromatids of each pair of homologous chromosomes are now visible. Figure \(\PageIndex{1}\): Crossover between homologous chromosomes: Crossover occurs between non-sister chromatids of homologous chromosomes.
