What helps ensure the survive of a species?
Genetic variation. That is this variation the is the essence of evolution. Without genetic differences amongst individuals, "survival of the fittest" would not it is in likely. Either all survive, or all perish.
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During prophase I, chromosomes condense and also become visible inside the nucleus. As the nuclear envelope begins to break down, homologous chromosomes move closer together. The synaptonemal complex, a lattice that proteins between the homologous chromosomes, forms at certain locations, spreading to cover the whole length the the chromosomes. The chop pairing of the homologous chromosomes is called synapsis. In synapsis, the gene on the chromatids of the homologous chromosomes room aligned through each other. The synaptonemal facility also supports the exchange of chromosomal segments in between non-sister homologous chromatids in a procedure called crossing over. The crossover occasions are the an initial source of hereditary variation produced by meiosis. A single crossover event in between homologous non-sister chromatids leader to one exchange of DNA in between chromosomes. Following crossover, the synaptonemal facility breaks down and also the cohesin connection between homologous pairs is likewise removed. At the finish of prophase I, the pairs are organized together only at the chiasmata; lock are called tetrads due to the fact that the four sister chromatids of every pair of homologous chromosomes are now visible.
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