Biology Lab 2

Hardy-Weinberg Law

Equation that allows us to predict gene and
genotype frequencies in population -- that isn’t
evolving.
p^2 + 2pq + q^2 = 1
allele frequencies will not change from one generation to the next, if certain assumptions are met
1)Mating is random across the entire population.
2) All genotypes have equal viability and fertility (no selection for or against one genotype).
3) Migration into the population can be ignored.
4) Mutation does not occur, or is so rare it can be ignored.
5) Population is large enough that the allele frequencies do not change from generation to generation due to chance (random genetic drift).
6) Allele frequencies are the same in females and males

cause deviation
Nonrandom Mating
➢ Gene Flow (Migration)
➢ Mutation
➢ Natural Selection
➢ Genetic Drift
We’ll focus primarily on Natural
Selection and Genetic Drift as
mechanisms that drive evolutio

Evolutions:

Change in allele (or genotype) frequencies over
generations

chi square value try questions but also

x^2=sum (observed-expected)^2/expected

p-value (p): the probability that H₀ is true (results due to natural variation)
• α-level: threshold p-value that determines if results are significant or not

A high p value means there is a high probability that what we are seeing is due to natural variation (accept Ho not significant)
A low p value means there is a low probability that what we are seeing is due to natural variation (reject Ho, significant)
We are using an α-level of 0.05 or 5% to determine significance
• If p>0.05 → more than 5% chance that what we see is due to
natural variation alone (accept H₀, not significant)

Degrees of Freedom (df): number (n) of categories/traits minus 1
df= (n) -1 = n-1= 3 (AA, Aa, aa) - 1 = 2

If X²calculated < X² critical, there is a >5% chance (p>0.05) that frequencies are just due to variation(accept H₀, not significant)
• If X²calculated > X² critical, there is a

variables

sample Size (n): the number of specimens or replicates in your experiment
• Our Sample Size (n): 50 individuals
• Null Hypothesis (H₀): Any patterns/ variation in data are caused by natural variation, and not by experimental treatment
• Our Null Hypothesis (H₀): Evolution is not occurring, follows Hardy-Weinberg estimation
• Alternate Hypothesis (H): The variation in the data is due to the treatment, not natural variation
• Our Alternate Hypothesis (H): Evolution is occurring, does not follow Hardy-Weinberg estimation

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