Exercise 2_Hardy-Weinberg_Modified

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Feb 20, 2024

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Student Name: 1- All answers must be in blue 2- Make sure that you watch my lecture video on this topic Exercise 2: Hardy-Weinberg Equilibrium (Natural Selection) Introduction: If you live in an urban or suburban area of North America, you are probably familiar with the eastern gray squirrel ( Sciurus carolinensis ). The black squirrel is a melanistic subgroup of this species. This black variant can be born to gray parents and is the result of a mutation that causes more melanin to be concentrated in their hairs. Offspring born from these mutants are more likely to inherit the trait because it is a dominant allele . Recall that evolution is a change in the frequency of alleles within a population over time . If you were to go to some areas of North America, you might observe that there were more black squirrels than you would find in other areas. 1- Is this evidence that the squirrels are evolving? To determine if evolution has occurred, biologists compare the allele frequencies in a population . If no evolution has occurred, then the alleles for each type of fur would occur in the same frequency. 50% would have the B allele and 50% would have the b allele. Problem, each individual contains two alleles for a trait, so we must use math to determine the allele frequencies. The Hardy-Weinberg Equation is used to determine the allele frequencies and whether those frequencies have remained constant. In any case, where the allele frequencies have changed, then evolution has occurred . Hardy-Weinberg Equations p 2 + 2pq + q 2 = 1 p + q = 1 p = frequency of the dominant allele in the population q = frequency of the recessive allele in the population p 2 = homozygous dominant individuals q 2 = homozygous recessive individuals 2pq = heterozygous individuals Part 2: Explaining Hardy Weinberg Equilibrium - Khan Academy https://www.khanacademy.org/science/biology/her/heredity-and-genetics/v/applying-hardy-weinberg ~ 5 minutes Watch the video which shows how the HW equation is applied.

In the example used, if 9% of the population has blue eyes , what are the following values: q 2 q = p = p 2 2pq How many in the population have the following genotypes? BB Bb bb Part 3: Field Data Collection You decide to find out if the black squirrels you are seeing in Bushytail Park are evidence of evolution. You go out for a day to document all the squirrels in the park and their coloration. Your careful data collection and documentation reveal an estimate of the squirrels in the park. Squirrel Data at Bushtail Park Gray Black Number of squirrels 39 14 But how can these observations tell you what the allele frequencies are? The H-W equation needs to be set up based on the number of recessive alleles that can be observed. You can determine this number based on the individuals that display the recessive trait. All the gray squirrels in the park are genotype bb, but all the black squirrels can be BB or Bb. 1. Calculate the frequency of individuals that display the recessive (bb) trait by dividing the number of grey squirrels by the total number of squirrels. Number of gray squirrels Total number of squirrels Frequency or q 2 2. Now that you know q2, you can determine what q is by taking the square root of that number

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