BIOA01H3 Chapter Notes - Chapter 21: Molecular Clock, Pseudogene, Genetic Drift
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Sharan Chinniah BIOA01
Fates of Mutations:
1. Fixation: mutation is maintained within the population.
2. Intermediate: mutation is maintained at an intermediate through balancing selection.
3. Elimination: mutation is eliminated through natural selection or genetic drift.
Molecular Evolution: The accumulations of mutations which leads to the gradual alteration of
DNA sequences in the preceding generations.
• Genetic Isolation: Members of one species cannot exchange genetic material with
members of another species.
o Eg. Humans and chimpanzees had a common ancestor 7 million years ago;
however, over time mutations specific to each arose isolating the two.
• Genetic Clock: The correlation between the amount of time two species have been
evolutionary separated and the amount of genetic divergence between them.
o The rate of molecular clock varies between genes.
o Pseudogene: A gene which is no longer functional.
▪ Pseudogene molecular clocks progress at fast rate because all mutations
that occur are neutral.
REVIEW: Pg. 422
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