Question

Meiosis is an essential event in the sexual life cycle of an organism. Give the reasons.

Answer 1

Hint:Meiosis is defined as a specialized type of cell division that is present in special types of cells at a specific period. It is observed in diploid germ cells of the sex organs. In this type of cell division, the cell divides two times and possesses half the number of chromosomes.

Complete answer:
Meiosis shows resemblance with two mitotic divisions without an intervening period of DNA replication. There are two types of meiotic division present. In the first meiotic division the reduction of chromosome number takes place and as a result two haploid cells are resulted by this division. First meiotic division is also termed as the heterotypic division.

In the second meiotic division, haploid cells divide mitotically and give rises to four haploid cells. The second meiotic division is also termed as homotypic division.

In the homotypic division pairing of chromosomes, exchange of genetic material and reduction of the chromosome number do not know to occur.

Both the meiotic divisions take place through four usual stages of the meiosis, namely Prophase, metaphase, anaphase and telophase. The prophase of the first meiotic division is Very important because the most cytogenetical events such as crossing over, synapsis, etc., takes place during this phase.

Meiosis has the greatest significance for the biological world and during sexual reproduction. Some of them includes:
i) The meiosis maintains and provides a definite and constant number of the chromosome in the organism. When gametes are formed due to the meiosis, the number of chromosomes is halved. So, it ensures that each gamete will have one pair of chromosomes. Later the haploid gamete Fuse with the complementary haploid gamete and results in formation of diploid zygote (2n). Hence, the number of chromosomes is maintained.

Note: By crossing over (that is the process exchange of genes between homologous chromosomes, resulting in a mixture of parental characteristics in offspring) The meiosis provides opportunity for the exchange of the genes and so it is the cause of the genetic variations among the species. The variations are usually the raw material of the evolutionary process.