genetic variation

• what are two ways genetic variation is introduced?

  crossing over and independent segregation
• independant segregation

  • when homologous pairs line up randomly at the equator and seperate
• how do you find the number of genetically different gametes produced by independant segregation ?

  2 to the power of n

  n is the number of homologous chromosome pairs
• meiosis involves two nuclear divisions and creates 4 genetically different haploid cells from a single diploid parent cell
• in meiosis 1 the homologous pairs are seperated

  in meiosis 2 the sister chromatids split
• variation occurs in meiosis 1
• further variation introduced when a random sperm and egg fuses so its (2^n)^2
• describe crossing over and how it leads to genetic variation?

  • homologous pairs form a bivalent
  • they twist and form a chiasma
  • alleles are exchanged
  • produces a new combination of alleles