Theme 4B Flashcards
(12 cards)
Population
- Interbreeding group of individuals that belong to the same species and live within a restricted geographical area
Population Inheritance vs. Mendel Inheritance
- Frequency (f) of an allele in a pop is often not the same as ratio in a single cross
Population Genetics
- Shift from individual to population lvl thinking
- f of an allele in a pop is often not the same as the ratio in a single cross
Darwin’s Conditions for Evolution
- Individuals within a species VARY
- Some variation is passed to offspring (heritable)
- More Offspring are produced than can survive and/or reproduce
- Survival and reproduction is NOT RANDOM, but related to phenotypic variation
When will evolution by nat sel not occur?
- No variation
- Variation NOT heritable
- Variation heritable but has no fitness consequence
What happens to genetic variation in absense of evolution?
- Genetic homogeneity among individuals
How to Test Hypothesis?
First thing you develop?
Null hypothesis
GH Hardy & W. Weinberg Hypothesis
- What happens to single trait, at a single genetic locus, that is encoded by 2 alleles, in the absense of evolution?
- If nothing acting on trait, should be stable
Conditions for Absence of Evolution
Hardy Weinberg Conditions
- Single Locus with 2 alleles doesn’t change state b/w gens (no mutation)
- Alleles not added/subtracted to pop (No gene flow from other pops)
- Pop is very big (infinite in theory): Removes random processes (kills drift)
- Nat sel doesn’t affect alleles considered (all individuals have same fitness)
- Random mating (same fitness)
For 4 - Porbability of surviving to breed the same, mating and fertilizing ability the same
Genetic Drift
- Allele f can change by chance alone given the # of matings that can occur when you have a low # of individuals copared to a large # of individuals
With a bowl of 5 colours and 20 M&Ms, if you take a handful of 5 the chance they are all the same colour is small, you trastically changed the ‘genes’ present. In a pop of 2000 M&Ms the change is relatively inconsequential.
Hardy-Winberg Equilibrium
- Conditions for absense of evolution met
- Allele f doesn’t change over time
- Pop allele shown via p & q, p =freq(A), q = freq(a)
- p + q = 1
- Use Mendelian probability theory - P(event 1 & event 2) = P(event 1) x P(event 2) if events independent
What does a departure from equilibrium suggest?
That one or more of the HWE assumptions has NOT been met
