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genetic variation

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Introduction

Fion Lai 13 C The significance of meiosis in generating genetic variation Meiosis is undergone to produce sex cells (gametes). It consists of two divisions. The first division includes the separation of homologous chromosomes. This part of the division allows crossing over and swapping bits of chromatids and this leads to shuffling of genes so that the sex cells produced are genetically unique. The second division includes the pulling apart of chromatids. This produces four haploid nuclui, each with one copy of each homologous chromosome. But why is it essential to have genetic variation in gametes? Theoretically, a species of organism may survive in the same body form in an unchanging environment for millions of years. ...read more.

Middle

Also, new combinations of alleles are produced, and these may give rise to individuals with new features that favour their survival. The survivors then pass on their successful gene combinations to their offspring and modify their species. In short, genetic variation allows diversity within populations upon which natural selection can act. In germs, recombination at meiosis plays an important role in the repair of genetic defects. It helps maintain the existence of the germ line possibly by the removal of faulty RNA and protein molecules, or by the elimination of defective germs. There are three sources of variation. A. Independent assortment In each homologous pair, one chromosome is derived from the original female parent and one from the male. ...read more.

Conclusion

Crossing over Even more variation is introduced during prophase1 by a process called crossing over. Once a homologous pair of chromosomes has formed a bivalent, two of the chromatids coil together. When the chromosomes separate again during anaphase, parts of the chromatids are swapped from one chromatid to another. As a result, the new chromatids have some sections that have been copied from the maternal chromosome and some from paternal chromosome. In conclusion, there are three sources in increasing genetic variation in meisos; new combinations of alleles result from independent assortment of the maternal and paternal chromosomes; from crossing over of sections of chromatids; and from random fertilization. All of them are very essential as to maintain the existence of organisms. ?? ?? ?? ?? 1 ...read more.

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