People with complete achromatopsia have difficulty in seeing detail (lines 2–3) - AQA - A-Level Biology - Question 10 - 2018 - Paper 1

To calculate the percentage of heterozygous individuals using the Hardy-Weinberg equation, we denote:
Let p = frequency of the dominant allele, and q = frequency of the recessive allele.
Since 10% of the population is affected with achromatopsia, this corresponds to the frequency of the homozygous recessive genotype (q²). Therefore,
$q^2 = 0.10$
To find q, take the square root:
$q = ext{sqrt}(0.10) ext{ which is approximately } 0.316$
Using the relation p + q = 1,
$p = 1 - q = 1 - 0.316 ext{ which is approximately } 0.684$
The percentage of heterozygous individuals (2pq) can be calculated as:
$2pq = 2 imes p imes q = 2 imes 0.684 imes 0.316 ext{ which is approximately } 0.432$
Thus, approximately 43.2% of the population are heterozygous for this disorder.

Red-green color blindness is linked to the X chromosome. Males have one X and one Y chromosome, while females have two X chromosomes. A single recessive allele on the X chromosome will cause color blindness in males. In females, two copies of the allele are needed for the condition to manifest, making it less frequent in females.

People with red-green color blindness usually lack functioning green or red-sensitive cones. This absence or malfunction prevents them from detecting and differentiating between red and green wavelengths of light, leading to difficulty in distinguishing between these colors.

Induced pluripotent stem (iPS) cells could potentially differentiate into functional photoreceptor cells (cones) that are capable of sensing red and green wavelengths. These newly developed cones could then be integrated into the retina, restoring the ability to perceive color.

The use of iPS cells may offer long-term solutions by providing a continuous source of functional cones, unlike gene therapy, which may only provide a temporary fix. Additionally, iPS cells can be created from a patient's own tissues, minimizing the risk of rejection or immune response. Furthermore, they allow for the possibility of repeated treatments, enhancing effectiveness.