Question

The ability to taste PTC is due to a single dominate allele "T". You sampled 215 individuals in biology, and
determined that 150 could detect the bitter taste of PTC and 65 could not. Calculate the frequency of the
heterozygous genotype.




a
17%
b
72%
c
50%
d
34%

Answer 1

To determine the frequency of the heterozygous genotype for the PTC tasting, we can use the Hardy-Weinberg principle. Here are the steps involved in the calculations:

1. **Determine the frequency of the dominant (T) and recessive (t) phenotypes**:

- Taster (TT or Tt): 150 individuals
- Non-taster (tt): 65 individuals
- Total individuals = 215

2. **Calculate the frequency of the recessive phenotype (tt)**:

\[
q^2 = \frac{\text{Number of non-tasters}}{\text{Total individuals}} = \frac{65}{215} \approx 0.3023
\]

3. **Calculate \( q \)** (the frequency of the recessive allele):

\[
q = \sqrt{q^2} = \sqrt{0.3023} \approx 0.55
\]

4. **Calculate the frequency of the dominant allele (p)**:

\[
p = 1 - q \approx 1 - 0.55 = 0.45
\]

5. **Calculate the frequency of the heterozygous genotype (Tt)**:

Using the Hardy-Weinberg equation \( 2pq \):

\[
2pq = 2 \times p \times q \approx 2 \times 0.45 \times 0.55 \approx 0.495
\]

6. **Convert to percentage**:

\[
0.495 \times 100 \approx 49.5\%
\]

Rounding this to the nearest whole number gives approximately 50%.

Therefore, the frequency of the heterozygous genotype (Tt) is approximately:

c. 50%