Where are we going with this? The information on this page should increase understanding related to this standard: Identify chronological patterns of change and communicate that biological evolution is supported by multiple lines of empirical evidence that identify similarities inherited from a common ancestor (homologies).
So… In a population of 100 turtles if…64 turtles are “BB”12 turtles are “Bb”24 turtles are “bb”Then we can figure out the frequency of B and b (which is the allele frequency). How many B's are there? How many b's are there?Math… then, we can say that the B allele frequency is 70% and the b allele frequency is 30%.
The Hardy-Weinberg Principle states that allele frequencies in a population will remain constant under 5 conditions:
- No natural selection occurs in a population.
- No migration into or out of a population (no gene flow).
- No mutations happen in the gene pool of a population.
- Random mating throughout the population.
- Large populations of organisms to keep frequencies constant.
Hardy-Weinberg Equations for Genetic EquilibriumWhere "frequency" is expressed as a decimal representing how many there are compared to the total number and where…
p = frequency of dominant allele (A)q = frequency of recessive allele (a)
p + q = 1
p2 + 2pq + q2 = 1
will also be true so that…
2pq = frequency of heterozygous organisms (Aa)p2 = frequency of homozygous dominant organisms (AA)q2 = frequency of homozygous recessive organisms (aa)
q2 = 36% = .36
p + q = 1p + .6 = 1p = 1 = .6p = .4
p2 = .16
2pq = 2 • .4 • .62pq = .48
p2 + 2pq + q2 = 1.16 + .48 + 36 = 1
(These add to 1)
(These add to 1)
- This principle provides a baseline to compare actual populations to.
- Step 1: Find allele frequencies in year 1
- Step 2: Find allele frequencies in year 5
- If a population is in genetic equilibrium, then the allele frequencies from Year 1 would equal Year 5. If Year 5 shows different allele frequencies, then we know that genetic drift is happening, and we can find out how much a population has changed.
- With this information, we can see how quickly a population is changing.