Question

Explain what accounts for phenotypic differences among siblings following meiosis

Answer 1

Meiosis is a type of cell division takes place to produce gamete haploid cells from the diploid somatic cells. Following meiosis, gametes are produced. Then the male and female gametes fertilize to form the zygote. Meiosis causes genetic variations among the offsprings of the sexually reproduced parents.

Following are the reasons which are responsible for the phenotypic variation among the offsprings produced by meiosis and sexual reproduction -

1. Crossing over

Crossing over takes place in the prophase I of meiosis I. During crossing over the genetic materials are exchanged among the one chromatids of the homologous chromosomes. (homologous chromosomes are the two sets of a chromosome which are inherited one from mother and other from father). Thus after the crossing over the two chromatids have different sets of genes and two other chromatids have a similar set of genes as of the parents (one maternal and other paternal).

2. Haploid cell and Random Chromatid Assortment

After the meiosis the cell formed is haploid, the two haploid cells fertilize to form a diploid zygote. Here, during the meiosis when the chromatids are separated among the daughter cells, this takes place randomly and does not follow any pattern. Thus, the daughter cells formed may have few maternal chromatids and rest others paternal chromatids.

Generally, during the meiosis II when the sister chromatids are separated in the two poles of the cell, this distribution of the chromatids takes place randomly and thus the daughter cells produced have a different composition of chromatids in terms of the paternal and maternal chromatids.

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