Recombination, Mutation, Genetic Drift, Gene Flow

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Recombination, Mutation, Genetic Drift, Gene Flow

• Also evolution ?

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Recombination

• Remember Meiosis?
• This is when recombination occurs
• Shuffling of chromosomes/genes/alleles
• Also crossing over
• Remember fertilization?
• Coming together of shuffled genes
• New alleles not created, just
• rearranged for more genetic variability

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Mutations

• Creates new alleles
• Beneficial, neutral, or lethal
• Passed on to new generations if they arise in
  gametes
• Can reduce chances of survival and reproduction

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• If it causes severe reductions, usually ends with
  death
• Neutral mutation changes base sequence but has no
  effect on survival or reproduction
• Beneficial mutation ex. corn plant has a
  mutation that makes it grow faster or larger
  giving it best access to sunlight and nutrients
• Neutral mutation might prove helpful if the
  environment changes

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Genetic Drift

• Random changes in allele frequencies over time
• Effect is greatest in small populations leads
  to loss of genetic diversity
• Allele will become more or less prevalent in
  small pops
• Bottleneck
• and Founder Effect

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Bottleneck

• Drastic reduction in population size because of
  severe pressure

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Founder Effect

• A few individuals establish a new population
• Unpredictable genetic shifts occur

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Gene Flow

• Physical movement of alleles into and out of a
  population
• Opposes the effects of mutation, natural
  selection, and genetic drift
• Keeps populations similar to one another
• Increases genetic variability in that new
  population

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Cladograms

• Aka. Phylogenetic tree, branching tree,
  evolutionary tree
• Lines not still apparent at present are extinct
• Do not have to all face the same way

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Hardy-Weinberg Principle

• Random mating
• Large population
• No movement
• No mutations
• No natural selection
• Allele frequency in a population will remain
  constant

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H-W Principle

• p2 2pq q2 1
• p q 1
• p2 frequency of homozygous dominant
• 2pq frequency of heterozygous
• q2 frequency of homozygous recessive
• p dominant allele
• q recessive allele

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H-W Principle

• 1 in 1700 US Caucasian newborns have cystic
  fibrosis. C for normal is dominant over c for
  cystic fibrosis.
• What percent of the above population have cystic
  fibrosis (cc or q2)?
• What percent of the population do not have cystic
  fibrosis and are homozygous dominant (CC or p2)?
• What percent of the population is heterozygous?