Tetrad is the four sister chromatids of the two chromosomes of the homologous pair or the bivalent. Here, the chromatids, which belong to the opposite chromosomes of the homologous pair, can undergo recombination through chromatid crossing over.
Note that the chromatids that are capable of undergoing crossing over are the non-sister chromatids. Importantly, the homologous recombination is responsible for exchanging parts of chromosomes, and these exchanged parts pass into different gametes.
Hence, it is the main process of producing genetic variation in successive generations. Chromatid pair is the two chromatids of a chromosome that has undergone DNA replication. Basically, the two chromatids formed from the same chromosome are sister chromatids. As mentioned above, DNA replication occurs during the S phase of interphase, which prepares the cell for subsequent cell division.
In this process, the replicated chromosomes condense during the metaphase I of the meiosis I. And, these are visible under the light microscope during this step as thread-like structures. Moreover, the DNA replication occurs in both types of cell divisions; the mitosis and meiosis, in order to double the amount of DNA in the nucleus. The replicated chromosomes tend to condense during metaphase I of meiosis I.
The two sister chromatids are held together by cohesion proteins through the subsequent steps of cell division. Tetrad has the same genes but different alleles. Besides that, they occur during the first prophase of meiosis. The chromosome should have the same length, centromere position, and staining patterns. Homologous chromosomes have the same genes. I am dynamic and vocal in my teaching and would use unseen past paper questions and worksheets to effectively teach the information needed for success in your exams, including test skills that will maximise your points and capabilities!
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