LECTURE 2

Mutations: the source of variation

Today's topics:

  1. Point mutations
  2. Insertions and deletions
  3. Crossovers and recombination
  4. Gene deletions and duplications

Readings:

Pierce: 473-479, 482, 235-253
Stearns and Hoekstra: 515-516

Mutations

Locus


Mutation


Germ-line vs. somatic mutations



"Random" mutations?




Point mutations

Single nucleotide substitutions



Allele

polymorphic

monomorphic








"wild type" allele


"mutant" allele

"variations"

Polymorphic point mutation sites are called SNPs





Transition mutations



Transversion mutations







Why are transitions more common than transversions?


see Figure 15.10

Silent (synonymous) mutations


Nonsense mutations


Missense (nonsynonymous, replacement) mutations

Examples







Insertions and deletions

The insertion or deletion of a base will cause a frame shift.




Chromosomal mutations






  1. Chromosomal rearrangements



    1. Duplication
      1. Tandem duplication



        motif




        SSR / microsatellite / minisatellite





        DNA fingerprinting



      2. Displaced duplication

      3. Reverse duplication

    2. Deletion


    3. Inversion
      1. Paracentric inversion

      2. Pericentric inversion






      formation of loops during cell division






        • no crossover



        • crossover in an inversion loop






    4. Translocations
      1. Reciprocal translocation

      2. Nonreciprocaal translocation

      3. Robertsonian translocation




  2. Changes in chromosome number


    1. Aneuploidy

    2. Polyploidy





Recombination






For next time:

Pierce: 47-58

Stearns and Hoekstra: 510-515