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Final

BISC 102 Final: Study Notes - Lectures 11-13
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Department
Biological Sciences
Course Code
BISC 102
Professor
Erin Barley

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Lec 11: Genetics II
1. Gregor Mendel (1822-1884)
- Interested in inheritance
- Pea plants: easy to grow + breed, 7 characteristics with discrete traits
- He noted “factors” [genes] were discrete, heritable, produced predictable ratios
- Most phenotypic characters much more complex than Mendel’s pea characteristics.
2. Pedigrees
- X chromosome larger and has more genes than Y
- Assume dominance, X-linked
- Autosomal dominant: at least one parent is affected, every generation
3. Correcting misconceptions about dominant + recessive alleles
- Dominant + recessive alleles equally likely to be passed on, both expressed. Frequency of an allele is
independent of whether it is dominant or recessive.
Lec 12: Population Genetics
- Study of allele frequencies + changes to allele frequencies in populations
- Can predict genotype frequencies from allele frequencies (if not evolving)
- Genotype (C^R C^R), observed (320), HW (p^2), proportion (.8^2), expected (proportion x total of all
observed), (O-E)^2/E
- Frequency of alleles. Ex. f(C^R) = p = [2(320) + 160]/3(500). p + q calculated from observed.
- Observed = expected ----> hardy-weinberg equilibrium
- HWE = null model. X^2 < 3.84
Lec 13: Microevolution
- Evolution at the level of alleles
- Evolution = change in allele frequency in a given population over time.
1. Causes of change in allele frequency?
- Natural selection
- Genetic drift
- Gene flow
2. How do new alleles arise in a species?
- Mutations
- Horizontal gene transfer
3. HWE assumptions (not evolving)
- No mutations
- Random mating
- No natural selection
- Large population
- No gene flow
4. 3 modes of natural selection? - Adaptive
- Directional selection (one phenotype more/less fit)
- Disruptive selection (both phenotypic extremes most fit)
- Stabilizing selection (both phenotypic extremes are least fit)
5. What is genetic drift? - Non-adaptive
- Change in allele frequencies due to chance events
- Random, not result of fitness advantages/disadvantages
- Effects strongest in small population that stays small
- Reduces genetic diversity in a population + can fix alleles
- Alleles fixed when it has a frequency of 1.0
6. Special case of genetic drift: Founder effect

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Description
Lec 11: Genetics II 1. Gregor Mendel (1822-1884) - Interested in inheritance - Pea plants: easy to grow + breed, 7 characteristics with discrete traits - He noted factors [genes] were discrete, heritable, produced predictable ratios - Most phenotypic characters much more complex than Mendels pea characteristics. 2. Pedigrees - X chromosome larger and has more genes than Y - Assume dominance, X-linked - Autosomal dominant: at least one parent is affected, every generation 3. Correcting misconceptions about dominant + recessive alleles - Dominant + recessive alleles equally likely to be passed on, both expressed. Frequency of an allele is independent of whether it is dominant or recessive. Lec 12: Population Genetics - Study of allele frequencies + changes to allele frequencies in populations - Can predict genotype frequencies from allele frequencies (if not evolving) - Genotype (C^R C^R), observed (320), HW (p^2), proportion (.8^2), expected (proportion x total of all observed), (O-E)^2/E - Frequency of alleles. Ex. f(C^R) = p = [2(320) + 160]/3(500). p + q calculated from observed. - Observed = expected ----> hardy-weinberg equilibrium - HWE = null model. X^2 < 3.84 Lec 13: Microevolution - Evolution at the level of alleles - Evolution = change in allele frequency in a given population over time. 1. Causes of change in allele frequency? - Natural selection - Genetic drift - Gene flow 2. How do new alleles arise in a species? - Mutations - Horizontal gene transfer 3. HWE assumptions (not evolving) - No mutations - Random mating - No natural selection - Large population - No gene flow 4. 3 modes of natural selection? - Adaptive - Directional selection (one phenotype more/less fit) - Disruptive selection (both phenotypic extremes most fit) - Stabilizing selection (both phenotypic extremes are least fit) 5. What is genetic drift? - Non-adaptive - Change in allele frequencies due to chance events - Random, not result of fitness advantages/disadvantages - Effects strongest in small population that stays small - Reduces genetic diversity in a population + can fix alleles - Alleles fixed when it has a frequency of 1.0 6. Special case of genetic drift: Founder effect - Small founder population compared to large parent population: lower diversity + different allele frequency compared with parent population - The smaller the founding population, more likely alleles different from those of parent population - Founding populations = small - Migration from parent population does not affect allele frequency in parent population 7. Special case of genetic drift: Bottleneck effect - High homozygosity - Population becomes small very quickly ---> allele frequencies may change due to chance events. 8. What is gene flow? - Non-adaptive - Movement of alleles among populations - Can increase/decrease fitness of population - Ie. great tit. Birds in west introduced to less fit genes from mainland great tit. 9. Mutations (harmful, neutral, beneficial). Types of mutations? - Point mutations - Gene duplication - Genome duplication 10. Point mutations: mutation of single base pair ---> changes single amino acid ---> chan
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