HELP on Hardy Weinberg Problem

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In summary, the conversation discusses a Hardy Weinberg problem involving the dominance of unattached earlobes over attached earlobes in a population of 500 individuals. The problem asks for the expected number of individuals who are homozygous dominant and heterozygous for this trait. Using the equations p^2+q^2=1.0 and p^2+2pq+q^2=1.0, the solution involves finding the frequency of the recessive phenotype (q), determining the frequency of the dominant allele (p), and then using these values to calculate the number of homozygous dominant and heterozygous individuals in the population.
  • #1
iluvcats
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HELP on Hardy Weinberg Problem!

Homework Statement



the allel for unattached earlobes is dominant over the allele for attached earlboes. in a population of 500 individuals 25% show the recessive pheontype. how many individuals woul you expect to be homozygous dominant and heterozygous for this trait?

Homework Equations



p^2+q^2=1.0
p^2+2pq+q^2=1.0

The Attempt at a Solution



q^2=.25
p^2+.25=1.0
p^2=.75
.75 x 500

p^2 =375 people are homozygous dominant


square root of .75 = .87
square root of .25 =.5
2(.87)(.5)
.87
.87 X 500 =435 people are heterozygous

this on one of my many attempts with this problem. i REALLY need some help with it. someone to walk me step by step through it. i know the equation, i have spent plenty of time working on it and i have more of the same problems so if i don't understand one of them than i can't do any. i have looked through all my textbooks and am unable to understand it. so if you could please help me out and help me step by step with so i can understand how to apply the formula to the problem i would really appreciate it. thank you
 
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  • #2
step 1: q^2 = .25 this is correct.

step 2: You need to know what q is. What is the square root of .25? Answer .50

step 3: You need to know p. The total is always 1.0. So p = 1.0 -q
which is p = 1.0 -.50
which leaves p = .50

step 4:We have p=.5 and q=.5
What percent are homozygous dominant (based on frequency of p)
p times p (from your equation above p^2 + 2pq + q^2=1.0) is the percent of
homozygous dominant - p^2 = .25
How many in the population: .25 x 500 = 125 dominant homozygous

step 5: We now need to know how many heterozygous. Since we know the percent of
homozygous recessive - it was given to us - .25 x 500 == 125 homozygous
recessive.
step 6: We have 500 total. We know 125 are homoz recessive another 125 are homoz
dominant. We used up 250. We have 500. So we are left with 250
heterozygous

So now you have template to work these problems.
 
  • #3
thank you VERY much for helping me. i understand it now. thank you. :)
 

1. What is the Hardy Weinberg principle?

The Hardy Weinberg principle is a mathematical equation that predicts the genetic makeup of a population from generation to generation. It states that in a large, randomly mating population with no genetic drift, mutations, gene flow, or natural selection, the allele and genotype frequencies will remain constant over time.

2. How is the Hardy Weinberg equation used?

The Hardy Weinberg equation is used to determine the expected frequency of genotypes in a population. It is also used to test whether a population is in Hardy Weinberg equilibrium, which can provide insight into the evolutionary forces acting on a population.

3. What are the assumptions of the Hardy Weinberg principle?

The assumptions of the Hardy Weinberg principle include a large population size, random mating, no mutations, no gene flow, and no natural selection. These assumptions are rarely met in real populations, but the principle can still be used as a null model for studying evolutionary processes.

4. How do you calculate allele frequencies using the Hardy Weinberg equation?

The Hardy Weinberg equation states that the frequency of alleles in a population can be calculated by squaring the frequency of one allele and adding that to the frequency of the other allele. For example, if the frequency of allele A is 0.6, the frequency of allele a would be 0.4, and the total frequency of alleles in the population would be 1 (0.6^2 + 0.4^2 = 1).

5. Can the Hardy Weinberg principle be applied to real populations?

While the assumptions of the Hardy Weinberg principle are rarely met in real populations, it can still be a useful tool for studying evolutionary processes. In fact, deviations from Hardy Weinberg equilibrium can provide valuable insights into the factors that are driving evolution in a particular population.

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