Question

Albinism is an inherited condition caused by a recessive alleles a. A is the dominant allele
for the normal condition. What are the gametophytes of individuals R and S?
A. R=AA, S= AA
B. R= AA, S= Aa
C. R= Aa, S=Aa
D. R= aa, S= aa.

Answer 1

Hint:-
● Albinism is an inherited disorder where there is little or no pigment melanin.
● The type and amount of melanin produced in the body determine the body color.
● Melanin also has a role in the development of optic nerves, so the people with albinism
show the presence of vision-related problems.

Complete step-by-step solution:-
● A pedigree tree is a family tree or chart which is represented by symbols and lines that
represent the family history of the person.
● In the pedigree chart, the symbols represent the people.
● The genetic relationships are represented by using lines.
● Pedigree is used as a visual tool for the documentation of biological relationships in families
and can also be used to determine the mode of inheritance of genetic diseases.
● The white square represents a healthy male.
● The white circle represents a healthy female.
● The shaded square represents the diseased male.
● The shaded circle represents the disease of the female.
● In the above pedigree, 1 st generation the shaded square represents the diseased male and the shaded circle represents the diseased female.
● Then their possible genotype is aa since albinism is a recessive disease.
● The normal female and male will have genotypes either Aa or AA.
● In the second generation, the left generation has 4 children. They are normal. They produce
3 females and one male R.
● The right generation has 4 normal generations. 2 females and 2 males.
● The genotype of the second generation will be Aa.
● In the third generation, 7 individuals are produced.
● In this population, one male is affected and one female is affected.
● The genotype of the affected person will be aa and normal from Aa.
● R and S belong to generation 2 and where all the individuals are normal.
● The genotype of R and S are Aa and Aa.
● The correct answer is option C,

Note:- A recessive allele is the one which when present with the dominant allele cannot express itself. In albinism, since it is a recessive condition, the disease can be expressed only in the homozygous
recessive condition.
In the heterozygous condition i.e. Aa the recessive a cannot express itself.