A certain gene in a tree species determines how long it takes for a seed to germinate. In one population, the alleles for this gene are [tex]$T_1, T_2,$[/tex] and [tex]$T_3$[/tex].

The numbers of individuals with each of the possible genotypes are shown in the table.

\begin{tabular}{|l|l|}
\hline Genotype & Number of individuals \\
\hline [tex]$T_1 T_1$[/tex] & 50 \\
\hline [tex]$T_1 T_2$[/tex] & 60 \\
\hline [tex]$T_1 T_3$[/tex] & 40 \\
\hline [tex]$T_2 T_2$[/tex] & 50 \\
\hline [tex]$T_2 T_3$[/tex] & 55 \\
\hline [tex]$T_3 T_3$[/tex] & 45 \\
\hline
\end{tabular}

What is the frequency of the [tex]$T_2$[/tex] allele?

A. [tex]55\%[/tex]
B. [tex]28\%[/tex]
C. [tex]36\%[/tex]
D. [tex]72\%[/tex]



Answer :

To determine the frequency of the T2 allele in the population, we need to follow a systematic approach. Here’s a detailed step-by-step solution:

1. Count the Number of Alleles:
Each individual has 2 alleles for the gene. Therefore, if we know the number of individuals of each genotype, we can calculate the total number of alleles in the population.

[tex]\[ \text{Number of alleles} = \text{Number of individuals} \times 2 \][/tex]

Below is the total number of alleles in the population:
[tex]\[ \text{Total number of individuals} = 50 + 60 + 40 + 50 + 55 + 45 = 300 \][/tex]
So, the total number of alleles in the population is:
[tex]\[ \text{Total number of alleles} = 300 \times 2 = 600 \][/tex]

2. Count the Number of T2 Alleles:
We need to account for all the T2 alleles present in each genotype category:

- [tex]\( T2T2 \)[/tex]: Each individual has 2 T2 alleles.
[tex]\[ 50 \text{ (individuals with } T2T2) \times 2 = 100 \text{ T2 alleles} \][/tex]
- [tex]\( T1T2 \)[/tex] and [tex]\( T2T3 \)[/tex]: Each individual has 1 T2 allele.
[tex]\[ 60 \text{ (individuals with } T1T2) + 55 \text{ (individuals with } T2T3) = 115 \text{ T2 alleles} \][/tex]

Adding these, the total number of T2 alleles in the population is:
[tex]\[ 100 + 115 = 215 \text{ T2 alleles} \][/tex]

3. Calculate the Frequency of the T2 Allele:
To find the frequency of the T2 allele, divide the number of T2 alleles by the total number of alleles and multiply by 100 to convert it to a percentage.
[tex]\[ \text{Frequency of } T2 = \left( \frac{\text{Number of } T2 \text{ alleles}}{\text{Total number of alleles}} \right) \times 100 \][/tex]
[tex]\[ \text{Frequency of } T2 = \left( \frac{215}{600} \right) \times 100 \approx 35.83\% \][/tex]

Therefore, the closest option to 35.83% is 36%.

Hence, the frequency of the [tex]\( T2 \)[/tex] allele is [tex]\( \boxed{36\%} \)[/tex].

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