Genetic diagram for the cross between two heterozygous parents for albinism and state the genotypic and phenotypic ratios.

Here are the answers to the questions:

i. Genetic diagram for the cross between two heterozygous parents for albinism and state the genotypic and phenotypic ratios.

Let 'A' represent the dominant allele for normal pigmentation.
Let 'a' represent the recessive allele for albinism.

Since albinism is caused by a recessive allele, a heterozygous parent will have the genotype 'Aa' and a normal phenotype (but be a carrier).

• Parental Genotypes (P1): Aa $\times$ Aa

• Parental Phenotypes: Normal (carrier) $\times$ Normal (carrier)

• Gametes: Each parent produces two types of gametes: A and a.

• Punnett Square:

  $$\begin{array}{|c|c|c|} \hline \text{Gametes} & \text{A} & \text{a} \\ \hline \text{A} & \text{AA} & \text{Aa} \\ \hline \text{a} & \text{Aa} & \text{aa} \\ \hline \end{array}$$

• Offspring Genotypes (F1): AA, Aa, aa

• Offspring Phenotypes (F1): Normal, Albino

• Genotypic Ratio: The genotypes are AA, Aa, and aa. The ratio is 1 AA : 2 Aa : 1 aa.

  $$\boxed{\text{Genotypic Ratio: 1:2:1}}$$

• Phenotypic Ratio: Individuals with AA and Aa genotypes will have normal pigmentation. Individuals with aa genotype will have albinism. The ratio is 3 Normal : 1 Albino.

  $$\boxed{\text{Phenotypic Ratio: 3:1}}$$

ii. Describe the observable characteristics (phenotype) of an individual with albinism and explain two challenges they might face due to their conditions.

• Observable Characteristics (Phenotype) of an individual with albinism: An individual with albinism typically has very pale skin, white or very light blonde hair, and light-colored eyes (often blue, grey, or sometimes appearing reddish/pink due to visible blood vessels in the iris). They lack melanin pigment in their skin, hair, and eyes.

• Two challenges faced by individuals with albinism:

  1. Extreme sensitivity to sunlight and increased risk of skin cancer: Due to the absence of melanin, which normally protects the skin from ultraviolet (UV) radiation, individuals with albinism are highly susceptible to severe sunburn. This lack of natural protection significantly increases their risk of developing skin cancer and premature aging of the skin.
  2. Vision impairment: The lack of pigment in the iris and retina affects eye development and function. This leads to various vision problems such as photophobia (extreme sensitivity to light), nystagmus (involuntary rapid eye movements), strabismus (crossed eyes), and significantly reduced visual acuity (poor eyesight). These conditions can make daily activities like reading, driving, or recognizing faces challenging.