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29 Cards in this Set
- Front
- Back
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Natural selection is a combination of... |
- Neutral random genetic drift - Determinative selection |
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Parameters of a Wright-Fisher population? |
- Single population (N) - Finite and constant N - Haploid N - Gametes randomly successful |
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Why is RGD stronger in smaller populations? |
- Less chance for "dilution" or assimilation. - Takes fewer individuals to impact a gene frequency. |
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Why does a bottleneck increase population divergence? |
In a WF population: Elimination of other alleles randomly (or by selective pressure) will make room for one allele to proliferate (regardless of selective advantage) |
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What is identity by descent (IBD)? |
When individuals have the same allele from the same ancestor. |
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Inbreeding Coefficient (f) |
- Used to measure genetic relationship between two individuals. - Probability two individuals are identical by descent. |
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Ne? |
- Effective population size. - The size of a W-F population needed to express the same rate of RGD as the real population. - Harmonic mean. |
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Coalescence |
- RGD viewed in retrospect. - Probability of a common ancestor for a specific allele. |
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What is Mendel's first law? |
Law of segregation. Alleles are split up and segregated into different gametes. Each gamete contains only one allele of a particular gene. |
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What is Mendel's second law? |
Law of independent assortment. Genes are "particulate" and independent of each other and do not blend. |
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Why does gene linkage violate Mendel's second law? (linkage disequilibrium) |
Some genes are located close together on the chromosome. Meaning that they have a low probability of being separated during crossing over. According to Mendel's second law, proportions of each allele should be predictable. |
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Hardy-Weinberg Principle Assumptions |
To assure stable allele frequency. No selection No mutation Large population |
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Hardy-Weinberg Equation |
(p^2)+2pq+(q^2)=1 Where: p = allele 1 frequency q = allele 2 frequency |
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What is the Neutral Theory? |
Most genetic substitutions are synonymous, meaning there is no chance in phenotype. Change is neutral. |
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What is the molecular clock? |
Genetic mutations occur at a constant rate across all species. |
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What is wrong with the molecular clock theory? |
Animals with shorter lifespans should have a faster mutation rate than bigger, longer living animals. |
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What was the solution to the flaw in the molecular clock theory? |
Mutations are mostly neutral, but have a slight bias towards deleterious mutations. Smaller populations of longer living animals mean deleterious mutations have a greater probability of fixation. |
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What did Moto Kimura theorise? |
That most mutations were medium sized, opposed to Fisher who said mutations were mostly small changes. |
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Kimura's Rule of Thumb? |
Outside of a small range, the impact of selection is much greater. |
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Homeobox Genes |
A set of homeotic genes present is almost all animal life. Often duplicated and diverged from the original. Makes for a wide diversity in structures. |
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Homeotic Genes |
Genes which regulate growth and body patterns |
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Other important Hox gene info: |
Temporally + specially collinear. The 3' end are expressed earlier in development and are anterior on body plan. Present in precambrian explosion. |
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Ontogeny |
Embryogenesis/development |
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Ontogeny recapitulates phylogeny |
Haeckel Embryos still show remote ancestral features during development. Similarities even in distant relationships. Not quite true, or how Haeckel hypothesised anyway. |
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Heterochrony |
Change in developmental rate of an individual |
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Peramorphosis |
Accelerating development "Skipping" stages |
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Paedomorphosis |
Retardation/delayed development |
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Batesian mimicry |
Model is unpalatable Mimic population smaller and has to be smaller otherwise the system would fail. Negative frequency dependant selection |
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Mullarian mimicry |
Both species are unpalatable/toxic Stuck in stalemate Populations more or less equal size Positive frequency dependent selection |
