Topic 2: Hardy-Weinberg equilibrium

Question 1

What is the Hardy-Weinberg eqilibirum?

Answer 1

• a mathematical expression that describes the expected genotype frequencies in a new generation
• HW predicts that there is no change, and that evolution does not occur (genotypes are at a fixed and constant state!)

Question 2

Why was hardy-weinberg developed?

Answer 2

• to answer the question, why, if we have dominant traits, do they not increase in frequency? why do we still have recessive traits?

Question 3

Will a dominant trait increase in frequency in a population over time?

Answer 3

No! Even though they are dominant, we still see recessive traits in a population

Question 4

what is the formula we use for allele frequencies?

Answer 4

p + q =1

where p is the frequency of the dominant allele in a population

and q is the frequency of the recessive allele in the population

Question 5

What is the formula we use for genotype frequencies?

Answer 5

p^2 + 2pq + q^2 = 1

where p^2 is the percentage of homozygous dominant individuals

q^2 is the percentage of homozygous recessive individuals

2pq is the percentage of heterozygous individuals

Question 6

if the numbers of each genotype are known, we ___________________ to determine frequency

Answer 6

divide by the total number of individuals

Question 7

to determine allele frequencies from genotype frequencies….

Answer 7

take the genotype frequency, + (frequency of heterozygous individuals/2)

Question 8

What are the 7 assumptions under Hardy-Weinberg equilibrium?

Answer 8

1. Sexually reproducing species (2 parents = child)
2. Each generation doesn’t overlap (breeds then dies)
3. Random mating
4. No mutation
5. no genetic drift (infinite population size)
6. No natural selection (doesn’t matter if alleles are dominant or recessive)
7. No gene flow (Closed population)

Question 9

Why is hardy-weinberg useful in biology?

Answer 9

-HW gives us a NULL HYPOTHESIS, something to compare our data to, and if it is statistically significant, we can determine if evolution is occurring.

Question 10

How do we determine the expected number within a population?

Answer 10

multiply the expected frequencies by the total number of people within our population

Question 11

If a population is not at equilibrium, how many generations are needed before it will reach an equilibrium state

Answer 11

it will take one generation of random mating to attain HW equilibrium

Question 12

Is microevolution connected to the change in allele frequencies or genotype frequencies?

Answer 12

Allele frequencies, as microevolution is the change in allele frequencies that occur over time within a population

Question 13

How does a model of a single locus and two alleles differ from a model of a single locus and three alleles?

Answer 13

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Question 14

Why was HWE the improper tool to use in the Pillal and Patel (2019) study on the cusp patterning phenotype?

Answer 14

• primarily, the limitations were the tooth cusps themselves, as well as the population.
• Tooth cusps: There are environmental factors that effect cusps, such as teeth grinding and malnourishment - so these phenotypic traits are not purely genetic, additionally, we don’t even know if the tooth cusps were under selection
• Population: was a small size, they excluded anyone who had ever had any dental work, population was not a closed system of infinite size