This week’s focus was all Hardy-Weinberg Equilibrium.

We learned the history behind the HWEQ equation, who discovered it, and how to properly use it. We also focused on the conditions necessary for HWEQ. We started out with defining some terms as they relate to Hardy-Weinberg:

• Gene-  DNA that determines a trait
• Allele – A variant of a trait (DNA)
• Dominant Allele – Shows a trait/phenotype, regardless of the other allele.
• Recessive Allele – An allele that only shows when paired with another recessive.
• Homozygous – A matching allele pair (PP, dd, hh, KK, etc.)
• Heterozygous – An unmatched allele pair (Pp, Dd, Hh, Kk, etc.)
• Evolution – Change in allele frequencies over time.
• Population – a localized group of interbreeding individuals.
• Gene Pool – The collection of all the alleles present in a population.
• Mutation – Creates variation/ new and novel traits. Always happening.
• Gene Flow – Movement of organisms into/out of a population, changes allele frequencies.
• Non-Random Mating – Causes sexual selection and sexual dimorphism.
• Genetic Drift – Random, chance events that change the gene pool.

After learning these terms, we went over the conditions necessary for a population to in HWE, listed below.

1. Random Mating
2. No Mutations
3. No Gene Flow
4. No Natural Selection
5. No Genetic Drift

As you can see, very few real-world populations are actually in HWE. What is the purpose of HWE then, if it fails to describe reality? This was an important question this week. Turns out HWE is best used as a null model- a control group.  If you calculate the allele frequencies for a population if it stopped evolving and changing altogether, you can then see how that population has evolved over time compared to the null model. We did a lab to try this technique out on Friday to see if we could achieve HWEQ amongst ourselves. No surprises, we couldnt.

HWE Equation: p^2 + 2pq + Q^2 = 1,     p + q = 1

Synthesis/Questions Going Forward

HWE seems to pull together everything we’ve been learning the past few weeks. It brings all the vocab and methods of evolution and types of alleles into play. This feels like the first relatively powerful tool we’ve received, akin to M1V1 = M2V2 in Chemistry. But how will we better mathematically describe populations and allele frequencies in the future? How will we better simulate reality? Are there ways to account for the things HWE must hold constant?

Big Idea #1

 ^ Polydactyly ^