Mutation

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Mutation

• An evolutionary mechanism in what group?
• The only source of new genetic information.
• Mutation any heritable change in the structure
  or amount of genetic material.
• Different levels of mutation
• DNA mistakes made during DNA replication
• Spontaneous (random)
• Only mutations occurring during meiosis can
  affect the next generation.

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Effects of a mutation Depends on how it affects
the functioning of the protein.
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Population genetics

• Is evolution taking place in a population?
• Evidence
• 1. Statistical analysis of phenotypic attributes
• 2. Change in allele frequencies.

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Human controlled crosses
One gene two alleles Probability of getting
particular genotypes Based on frequencies of
alleles Same cross can be depicted as (G g) x
(G g) (G g)2 G2 2Gg g2 Generalized
case (p q)2 p2 2pq q2 Hardy-Weinberg
equilibrium formula Allele frequencies ? 0.5 G
0.5 g Genotype frequencies ? Phenotype
frequencies So evolution can be defined as a
change in allele frequencies.
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In natural populations

• Alleles segregate into different games in the
  same way, but
• Individuals free to choose mates
• Genotypic and phenotypic frequencies dependent on
  allele frequencies.

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Information from individuals in Lab Section 2,
with no individuals added from Regis
population. . Hand clasping 15 dominant (L on R)
3 recessive (R on L) N 18 15/18 individuals
are either C/C or C/c 0.83 3/18 individuals ARE
c/c 0.17 Is the population sampled in genetic
equilibrium? Need to know the frequencies of C
and c. Then plug the frequencies into the
Hardy-Weinberg formula Represents one generation
of random mating q2 frequency of c/c 0.17 q
square root of q2 square root of 0.17
0.4123 P q 1 p 1 q 1 0.4123
0.5877 p2 2pq q2 1 (0.5877)2
2(0.5877)(0.4123) (0.4123)2 0.3454 0.4846
0.1700 1 P 0.3454 ½(0.4846) 0.5877 q
0.1700 ½ (0.4846) 0.4123
Observed p and q
Have frequencies of C and c changed after
one generation of random mating.
Expected p and q
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Try this problem

• Information from students in Lab Section 2.
• Free ear lobes 13 individuals
• Attached ear lobes 5 individuals
• Is the population, from which this sample was
  drawn, in genetic equilibrium?
• If so,
• Is one condition more advantageous than the
  other?
• Hypothesis?