Mutation

Mutation

A heritable change to the nucleotide sequence of a segment of an organism’s DNA

• Good - any mutation that provides an organism with a selective advantage by increasing its fitness

• Bad - any mutation that provides an organism with a selective disadvantage by decreasing its fitness

Evolution

• alleles can be introduced into a population, and natural selection acts on the resulting phenotypes

• if an allele provides a selective advantage, it is more likely to be passed on, allowing an organism to spread its genes throughout the population over time

Chromosomal mutations

Large-scale alterations to nucleotide sequences; can affect the structure and number of chromosomes in an individual

• Numerical disorders (aneuploidy) - involve an abnormal number of chromosomes (trisomy)

• Structural disorders - involve a change to a chromosomes structure (translocations - portion of one chromosome is transferred to another, inversions)

Point Mutations

Small-scale alterations to nucleotide sequences (usually consisting of a change to a single nucleotide

• Substitution - replacing one nucleotide in a DNA sequence for another, can have a silent, mis-sense or non-sense effect

• Deletions/Insertions - involve removing a nucleotide or adding an additional nucleotide to a DNA sequence → frameshift effect