Tetrads, also known as bivalents, form during the prophase 1 stage of meiosis when duplicated chromosomes, each composed of two identical chromatids, pair up and complete the process of crossing over in which one chromos... More »

The major difference between prophase I and prophase II is the genetic recombination process that occurs during prophase I, but does not repeat in prophase II. During prophase I, the duplicated homologous pairs line up a... More »

In prophase I the nuclear envelope disintegrates, and the chromosomes within condense and cross over. In prophase II there are half as many chromosomes, and these are sometimes already condensed from the previous process... More »

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A tetrad is a composition of four chromatids that are formed after synapsis occurs during the prophase I stage of meiosis I. Each of the tetrads contains two chromosomes, known as a homologous chromosome pair, with two c... More »

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As explained by DevBio, nondisjunction is what happens when a pair of chromosomes do not separate properly during meiosis. According to Indiana University-Purdue University Indianapolis (IUPUI), nondisjunction can occur ... More »

"Crossing over" in meiosis refers to the process by which segments of DNA on nonsister, or homologous, chromatids break off and recombine on the other homologous chromatid. This process becomes a source of variation in e... More »

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The process of meiosis results in four cells that possess half of the chromosomes of the original cell. This occurs in cells that possess two chromosome sets, which happens in organisms that reproduce sexually. The cellu... More »