L06-Mutation

• The genetic substrate for natural selection and the raw material for evolution

  Mutation
• If there is no genetic variation neither genetic drift nor natural selection would be able to change allele frequencies, because there would be nothing to change
• Natural selection requires genetic variation upon which it could act
• change in genetic code

  mutation
• Nucleotide substitutions, insertions, deletions
• shuffling of combinations of alleles along a chromosome

  Genetic recombination
• Shuffling of combinations of haploid chromosomes into new genotypes

  Random mating
• At the Nucleotide level (Point mutations)

  substitution, Insertions, Deletion
• Single nucleotide substitutions

  transitions, transversions
• At the gene level mutations

  Gene insertions, Gene deletions, Exon shuffling
• At the chromosome level mutation

  Chromosome duplications, deletions, inversions, fusions
• At the genome level mutation

  autopolyploidization, allopolyploidization
• Within functional coding regions of the genome, mutations could have very different effects depending on where they occur
• Structural: changes in the actual coding region of the gene

  Primary: amino acid composition, secondary, tertiary, quaternary structure
• Regulatory: changes in gene regulation

  Gene expression
• Single nucleotide change

  Point mutations
• DNA replication error during Mitosis or Meiosis, Error in repair sites damaged by mutagens

  Point mutations
• Transitions are more common than transversions; that is, purines are more likely to mutate to purines, and pyrimidines to pyrimidines (transitions)
• The leading hypothesis is that because transition are mutations between nucleotides of similar structure, they cause less disruption of the DNA helical structure and are less detectable by DNA polymerase or mismatch repair enzymes
• purine to purine mutation

  transition
• purine to pyrimidine mutation

  transversion
• a type of point mutation in DNA where a single nucleotide change results in the creation of a premature stop codon within the coding sequence of a gene

  nonsense mutation
• type of point mutation in DNA where a single nucleotide change results in the substitution of one amino acid for another within the protein-coding sequence of a gene

  missense mutation
• a type of point mutation in DNA where a single nucleotide change occurs within the coding sequence of a gene, but it does not result in any change to the amino acid sequence of the encoded protein

  silent mutation
• also known as transposons

  jumping genes
• also known as missense mutation

  nonsynonymous mutation
• also known as silent mutation

  synonymous
• type of polyploidy in which an individual or species has multiple sets of chromosomes derived from a single ancestral species

  Autopolyploidization
• a type of polyploidy in which an individual or species has multiple sets of chromosomes derived from two or more different ancestral species.

  allopolyplodization
• the third base in a codon often referred to as the

  wobble position
• changing the third base of a codon does not result in a significant change in the amino acid incorporated into the protein
• Mutations that do not lead to amino acid change (often position 3)

  Synonymous substitutions
• Mutations that lead to amino acid changes (position 1,2)

  Nonsynonymous substitutions
• These are the common sources of new genes

  Gene duplications
• often followed by differentiation between the duplicates

  Gene duplications
• When gene duplication events occur and subsequent differentiation between the duplicates take place, they can give rise to what is known as a

  gene family
• a set of genes derived from a common ancestral gene through duplication events, and they typically share structural and functional similarities

  gene family
• Gene duplication could happen either due to "slippage" during DNA replication (gene copied twice), or unequal crossing over during genetic recombination during meiosis
• 0.01 duplications per gene per million years
• Half life for a gene

  3-8 million years