Recombination _ GeneConversion by sherrymirza

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									Recombination & Gene
     Conversion

               By:
Mirza Ahmed Hammad      1255
Bio-Informatics(M) 2007-2011




          By Mirza Ahmed Hammad
               Introduction

Recombination results in Gene Conversion
  during

• Meiosis Or

• Any event leading to Recombination e.g; DNA
  Repair
                  By Mirza Ahmed Hammad
      Types Of Recombination:
There are two types of recombination:

• Non-Homologous Recombination: Results in
  the insertion of new sequences or more
  frequently deletion of a part.

• Homologous Recombination: Results in new
  Recombinant and/or non-recombinant species
  also know as General Recombination
                  By Mirza Ahmed Hammad
Non-Homologous Recombination
         Overview:




          By Mirza Ahmed Hammad
      Homologous Recombination
             Overview:

There are three uses of Homologous
  Recombination in cells.

i. Accurately repairing double strand breaks.
ii. Handling fallen replication fork condition.
iii. Exchange bits of genetic information
     between two different chromosomes.
                    By Mirza Ahmed Hammad
           Homologous
          Recombination
           Mechanism:


             In this mechanism
               double strand
                 breaks are
            accurately repaired.


By Mirza Ahmed Hammad
      Effects of Recombination & Gene
                  Conversion
•   In humans, each meiosis requires that the starting cell keep track of 92
    chromatids, or 46 chromosomes resulting in four haploid sets.
•   Mistakes are especially common in human female meiosis, which arrests for years
    after diplotene: meiosis I is completed only at ovulation, and meiosis II only after
    the egg is fertilized. Indeed, such chromosome segregation errors during egg
    development are the commonest cause of both spontaneous abortion and mental
    retardation in humans.

•   Non-disjunction, aneuploidy & euploidy.
•   Down syndrome in humans, for example, which is the leading single cause of
    mental retardation, is caused by an extra copy of chromosome 21, usually resulting
    from non-disjunction during meiosis I in the female ovary.
•   Segregation errors during meiosis I increase greatly with advancing maternal age.
•   Despite its fallibility, almost all eukaryotes use meiosis, intermittently at least, to
    shuffle their genetic information before passing it on to the next generation.



                                    By Mirza Ahmed Hammad
By Mirza Ahmed Hammad


								
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