2.1: Agents of Evolutionary Change - Mutation

mutation

creates variation that may be heritable and can lead to evolutionary changes over time.

what are the agents of evolutionary change

mutation, gene flow, genetic drift, non-random mating, recombination and natural selection.

point mutation

single base change, insertion or deletion

insertion/deletion (indel)

DNA segments of different sizes are inserted/deleted into middle of existing sequence

frameshift mutation

when indel is not a multiple of 3 it shifts the reading frame of DNA sequence = changes amino acid sequence

large mutations

less frequent but often greater genetic consequences

• gene duplication/inversion

• chromosome fusion - chromosomes join together

germline mutation

• affects gametes

• transmitted via sexual reproduction

• create new variations (alleles) and can be inheritable

somatic mutations

affects all daughter cells of single cell (not gametes). not inheritable from parent to offspring

phenotypic effects

• neutral = no effect

• deleterious (negative) = natural selection can filter them out

• advantageous (positive) = natural selection favours

what happens if mutation rate is too low

no evolution as organisms will not be able to adapt

what happens if mutation rates are too high

too many functional elements would be disrupted and organisms would become less fit to environment

missense mutation

change in DNA causes an amino acid to be replaced by another one = often changing structure and function

nonsense mutation

change in DNA causes premature stop codon = truncated protein.

spontaneous mutations

permanent changes in genetic material without outside influence

• DNA replication errors

• chemical reactions

• meiotic errors

induced mutations

when an outside agent (mutagen) causes DNA changes that result in mutation

• some chemicals alter bases

• some chemicals add groups to bases

• radiation changes DNA

how do mutations relate to evolution

origin of genetic variation that can be acted upon by natural selection.

How did the discovery of the structure of DNA shed light on how variation is generated?

showed how genetic information is stored, replicated, and transmitted, highlighting mechanisms of mutation that create variations