What helps ensure the survival of a species?
Genetic variation. That is this variation that is the significance of evolution. Without genetic differences amongst individuals, "survival of the fittest" would not be likely. Either every survive, or all perish.
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During prophase I, chromosomes condense and become visible inside the nucleus. Together the nuclear envelope begins to rest down, homologous chromosomes relocate closer together. The synaptonemal complex, a lattice the proteins in between the homologous chromosomes, develops at certain locations, spreading to cover the whole length of the chromosomes. The chop pairing the the homologous chromosomes is dubbed synapsis. In synapsis, the gene on the chromatids the the homologous chromosomes are aligned with each other. The synaptonemal complicated also supports the exchange the chromosomal segments between non-sister homologous chromatids in a process called cross over. The crossover occasions are the very first source of hereditary variation created by meiosis. A single crossover event in between homologous non-sister chromatids leads to an exchange that DNA in between chromosomes. Adhering to crossover, the synaptonemal facility breaks down and also the cohesin connection between homologous bag is likewise removed. At the end of prophase I, the pairs are held together just at the chiasmata; lock are dubbed tetrads since the 4 sister chromatids of each pair of homologous chromosomes are now visible.
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