Polyploidy


Why would any species want to have more than one gene for any trait?

  • plants spontaneously undergo autopolyploidy,
    . . . a mechanism for creating more than one gene per trait,
    . . . with one gene for the trait per chromosome.

    In autoploidy, meiosis is interrupted

  • metaphase I is 2n chromosomes (aligned as pairs)
    . . -with 2 chromatids per chromosome
  • telophase, cytokinesis suspended
  • nuclear material is still
    . . -2n chromosomes,
    . . -2 chromatids per chromosomes
  • metaphase II is 2n chromosomes (aligned unpaired)
    . . -with 2 chromatids per chromosome
    . . -anaphase separates chromatids
  • telophase, cytokinesis suspended
  • nuclear material is now
    . . -4n chromosomes,
    . . -1 chromatid per chromosome
  • without cytokinesis,
    . . -cell returns to G-1
    . . -then S-1 with replication
  • nuclear material is now
    . . -4n chromosomes,
    . . -2 chromatids per chromosome
  • the plant is now 4n rather than 2n!


  • range of environmental conditions tolerated
    . . . can be broken into 2n+1 sub-ranges,
    . . . where n = number of genes or chromosomes.



    RETURN TO OUTLINE
    © 2004 Prof. LaFrance, Ancilla College