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Explain why the genetic variation that results from meiosis is different from the...

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sandali | Student, Grade 11 | Salutatorian

Posted June 24, 2010 at 2:33 PM via web

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Explain why the genetic variation that results from meiosis is different from the variation that results from mitosis.

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pamsuegun | Middle School Teacher | (Level 2) Adjunct Educator

Posted June 24, 2010 at 3:48 PM (Answer #1)

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A cell has chromosomes from 2 parents. During mitosis the cells make identical copies of themselves.  One  cell produces 2 daughter cells. The chromosomes duplicate themselves and separate in a way that each new daughter cell has the same type and number of chromosome as the original cell.  The only time that variation would occur is if there is a mutation or some type of foreign DNA is introduced by a virus or bacterium.  In meiosis the original cell divides into 4 cells and each cell has only half the number of chromosomes as the mother cell.   The chromsomes also sort independently so that the 4 cells have unique mixtures of the chomosomes that were in the original cell.  During meiosis a process called crossing over can occur where the chromosomes exchange sections to create chromosomes with new combinations of DNA.  This increases the variation produced by meiosis.   So in meiosis the products are cells that are unique and not like the parent cell. 

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aparajitasaraf | Student , Grade 10 | eNoter

Posted June 26, 2010 at 12:53 PM (Answer #2)

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A cell has chromosomes from two parents. Inside a cell during meiosis, the chromatin network condense to form thick chromosomes. These chromosomes duplicate forming two sister chromatids. The homologous pair of chromatis(i.e the chromosomes from mother and father) come closer to each other and exchange some genetic material this is known as chiasmata formation. This formation leads to variation and hence helps in evotion. This explains why you have some characteristics of your father and some of your mother. At the end of the meiosis four cells are formed which have half the number of chromosomes.

But in mitosis the chromosomes duplicated to form chromatids and they separate equally. There is no exchange of genetic material and hence the two daughter cells produced are exactly same as their parent cell.

 

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