In: Biology
sickle cell anemia is a recessive condition. Two diploid parents, heterozygous for sickle cell anemia produce 5 offspring. What is the probability that the parents have 3 or more children with sickle cell anemia? Using binomial distribution.
Sickle cell anemia is a recessive condition, hence requires two
alleles.
Normal (S) > Sickle-cell (s)
Normal genotypes = SS, Ss, sS
Sickle-cell genotypes = ss
Genotypes of the parents: Ss
As per Mendelian
Laws of Inheritance (Segregation, Independent Assortment, and
Dominance):
Probability of having sickle-cell child = 1/4
Probability of having normal child = 3/4
Number of ways in which 3 kids can be selected from a group of 5
kids = 5C3
Probability that the parents have 3 children with sickle cell
anemia = 5C3 (1/4)3
(3/4)2 = 90/1024 = 8.789%
Number of ways in which 4 kids can be selected from a
group of 5 kids = 5C4
Probability that the parents have 4 children with sickle cell
anemia = 5C4 (1/4)4 (3/4)1 = 15/1024 = 1.464%
Number of ways in which 5 kids can be selected from a
group of 5 kids = 5C5
Probability that the parents have 5 children with sickle cell
anemia = 5C5 (1/4)5
(3/4)0 = 1/1024 = .0976%
Probability that
the parents have 3 or more children with sickle cell anemia =
106/1024 = 10.351%