Respuesta :
Hey There!
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ANSWER:
[tex]\Huge{\textbf{MEIOSIS:}}[/tex]
Meiosis is a special type of cell division, which occurs only in the germ cells during the process of development and maturation to form gametes. It consists of two successive cell divisions,
- Meiosis 1 : First meiotic division, that reduces the NUMBER of chromosomes i.e. the parent cell is diploid(46 Chromosomes) and the daughter cells are haploid(23 Chromosome). It also causes genetic variation in the haploid by cross linkage.
- Meiosis 2 : Second meiotic division (Meiosis II) starts with two haploid parent cells and ends with four haploid daughter cells. Meiosis 2 like Meiosis 1, does not reduce the NUMBER OF CHROMOSOME that means the forming 4 daughter cells are haploid and their number of chromosome remains the same as the parent. BUT Haploid cells that go into the meiosis 2 have MORE AMOUNT OF CHROMOSOME THAN USUAL, thus MEIOSIS 2 REDUCES the amount of chromosome rather than the number of chromosome.
The DNA of the primitive germs cells is replicated prior to the meiosis 1 only and there is no replication of DNA before Meiosis 2. The four final cells reulting from the two meiotic divisions are not only haploid(i.e. containing 23 chromosome) but they are also containing 1n amount of DNA so that when the gametes fuse together forming a zygote, both the amount and number of chromosome and DNA remains SAME.
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[tex]\huge{\text{Why is Meiosis Important?}}[/tex]
Meiosis is essential for the sexual reproduction of eukaryotic organisms because it enables genetic diversity through recombination, and the repair of genetic defects.
It contributes in genetic reassorment which ensures the genetic diversity in the offsprings. The genetic reassortment takes place by following two mechanisms:
- During the prophase of meiosis 1, crossing over of genetic material between the homologous maternal and paternal chromosomes takes place which causes exchange of DNA fragments between the chromosome resulting is genetic diversity.
- During the anaphase of the first meiotic division, there is random distribution of maternal and paternal homologous chromosomes among the daughter cells which are produced as a result of meiotic division.
