CELL CYCLE AND CELL DIVISION: MEIOSIS ORREPRODUCTIONDIVISION:Meioum means to diminish,The type of cell division, in which the chromosome number is reduced exactly to half is called meiosis. The term meiosis was coined by J.B. Farmer 1905.It occurs in reproductive cells of sexually reproducing organisms.The cells in which meiosis occurs are called meiocytes.In meiosis the chromosomes present in meiocyte is reduced to half in Meiosis- I. & these reduced chromosomes divided by mitotically in Meiosis-II. In this the mother cell divides into four daughter cells and these cells are unidentical when compared to their parent cell.Every organism has definite number of chromosomes in diploid condition 2n. All organisms begin their life form at zygotic stage. The zygote is formed by the fusion of gametes. Thus in diploid organisms every cell has 2 sets of chromosomes each acquired from the male and female gametes. Chromosomes with similar characters, uniform size & types belonging to parental sources are called homologous chromosomes. In the life cycle of diploid organisms, the chromosome number is reduced to half at one stage or the other. If not, at every fertilization the chromosome number would be doubled leading to abnormal number & causes unimaginable genetic disorders. Since the number of chromosomes is reduced to half, it is called reduction division.
The key features of meiosis are. 1 Meiosis involves two sequential cycles of nuclear cell division called Meiosis I and Meiosis II but only a single cycle of DNA replication occurs. 2 Meiosis- I is initiated after the parental chromosomes have replicated to produce identical sister chromatids at the S-phase of interphase. 3 Meiosis involves pairing of homologous chromosomes & recombination between them. 4 Four haploid cells are formed at the end of Meiosis -- II.MEIOSIS- is divided in two; 1 Meiosis I. 2 Meiosis II
MEIOSIS-I is further divided into 1 Karyokinesis -- l ,2 Cytokinesis
MEOSIS II - is further divided into 1Karyokinesis II, 2 Cytokinesis
Karyokinesis-l: Occurs in four stages

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