in a population where you only know the total number of individuals with the dom

Question

in a population where you only know the total number of individuals with the dominant phenotype , how can you calculate the frequency of carriers and homozygous recessive individuals?

BIO-303 General Genetics Exam 2 Study Guide 17 Be sure you know how to determine allele frequencies in gene pools in simple 2 phenotypic classes in the population), as well as in more complex cases (eg possible at the locus), or when homozyogus mutants fall into multiple phenotypie random mating population) cases (2 alleles, and alleles ses (eg your three Are the genomes of all members of o papulation part of the gene pool? Why or The following represent the frequencies of individuals homozygous for a recessive allele (aa) in different local populations. Colculate the frequencies of the dominant (A) and recessive (o) population. Calculate the Population 1: 0.0064 a)p Population 2: 0.000081 caa) Population 3: 0.10 (aa) Pop 41o.oo40.084) 0.00008-0.009?4) Hotevo (2P4): 2(0,42) (0,08)=6,HE In a population where you know only the total number of individuals with the dominant phenotype, how can you calculate the frequency of carriers and homozygous recessive individuals? If 4% of a population in equilibrium expresses a recessive trait, what is the frequency of the recessive allele in the gene pool? What would be the expected frequency of heterozygotes in the population? What is the probability that two mated individuals who show the dominant phenotype, but for whom the genotype is unknown, will produce a child having the recessive phenotype?

Explanation / Answer

This question is based on Hardy-Weinberg equation.

The question says that in a population we know only the total number of dominant phenotypes. Using this data we need to calculate the frequency of carriers and homozygous recessive alleles.

Step 1

Let us consider that the total number of dominant phenotypes in a population is 16

As per the Hardy-Weinberg equation, we know that

p + q = 1 and p2 + q2 + 2pq = 1

where,

p = allelic frequency of the dominant allele

q = allelic frequency of the recessive allele

p2 = percentage of dominant individuals in a given population

q2 = percentage if recessive individuals in a given population

2pq = percentage of heterozygous individuals in a given population.

Step 2

From step 1, we know that the number of dominant alleles is 16.

Percentage of dominant allele = 16% = 0.16 = p2

So, from the above calculation, we obtained the percentage of dominant allele p2 = 0.16

Now we have to calculate the frequency of dominant allele p

p2 = 0.16

p = ?0.16 = 0.4

So, the frequency of dominant allele p = 0.4

Step 3

Now we shall calculate the frequency of recessive allele using the formula

p + q = 1

0.4 + q = 1

q = 1 - 0.4 = 0.6

So, from the above calculation, the frequency of recessive allele q = 0.6

Step 4

From steps 1,2 and 3 we know the frequency of dominant allele and recessive allele

Now we shall calculate the frequency of carriers

A carrier generally shows a heterozygous condition consisting of a dominant allele and a recessive allele.

So, the frequency of carriers in a population can be calculated by using the following formula

Frequency of carriers in a population = frequency of dominant allele x frequency of recessive allele

= 0.4 x 0.6

= 0.24

From the above calculation, frequency of carriers in a population is 0.24

Step 5

Since we already know the frequency of the recessive allele, we can easily calculate the frequency of homozygous recessive.

The homozygous recessive condition can be written as qq = q x q = q2

We know the value of q. That is q = 0.6.

So, q2 = (0.6)2 = 0.36

From steps 1 to 5, without knowing the population we calculated the following frequencies:

1. Frequency of dominant allele p = 0.4

2. Frequency of recessive allele q = 0.6

3. Frequency of carriers pq = 0.24

4. Frequency of homozygous recessive qq = 0.36

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