Question

explain why meiosis is more significant to evolutionary phenomena like variation, inheritance, etc.

Answer 1

Meiosis is the type of cell division which leads to variation among progeny and between progeny and parents. This is because it undertakes two events -

1. Crossing over between non sister chromatids of homologous chromosomes during prophase 1 of meiosis 1. In this phenomena, genetic material is exchanged between non sister chromatids. Each homologous chromosome contains two chromosomes, one from the paternal side and one from the maternal side. Crossing over, which is also known as recombination, between these two chromosomes results in the chromosomes which now contain some alleles of the paternal side and some alleles of the maternal side. Each chromosome therefore becomes a Recombinant chromosome.

( in mitosis there is no such process, there for each chromosome formed in the end is identical to the chromosome present in the parent cell)

2. Independent assortment of chromosomes of a homologous pair towards the opposite pole of the cell during anaphase 1 of meiosis 1. Each chromosome of a pair separate independently of the Other chromosome and move towards the opposite pole of the cell. Now each pole contains some chromosomes of the paternal side and some chromosomes of the maternal side.

( homologous chromosomes do not separate in mitosis, rather identical sister chromatids separate from each other and therefore the daughter cells formed in the under identical to Parent cell)

In this way the gametes formed in the end of meiosis 2 contains some chromosomes from the maternal side and some chromosome from the paternal side and also each chromosome contains some alleles from the maternal side and some alleles from the paternal side.

Please note that, when I say each chromosome becomes a Recombinant chromosome in point number 1, it doesn't mean that each chromosome is 50% parental and 50% maternal. After recombination a paternal chromosome contains a very few alleles of maternal chromosome and maternal chromosome contains a very few areas of paternal chromosome. Recombination occurs at a very small region and not throughout the chromosome.

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