Question

1.If approximately one in every 2500 white individuals in the united states is affected by the autosomal recessive disease cystic fibrosis, what are the frequencies of both the dominant and recessive alleles in the populations ?

If 14% of individuals in a population have the reseccive phenotype (aa), what percentage of the population is heterozygous ?

I need this answered with a legibale explanation step by step in a simple manner

Answer 1

Answer:

Based on the given information:

1) Proportion of individuals affected by autosomal recessive disease cystic fibrosis in US = 1/2500

Autosomal recessive disorder means that homozygous recessive genotype will be affected by disorder. Heterozygous individuals will be carriers and homozygous dominant will be normal.

Example let allele for cystic fibrosis condition be represented by F

• FF - Normal
• Ff - Carrier
• ff - affected

Frequency of dominant and recessive allele can be determined as below:

Formula used:

p + q = 1

p² + q² + 2pq = 1

• Proportion of affected individuals (ff or q²) = 1/2500 = 0.0004
• Frequency of recessive allele, f (q) = sqrt(0.0004) = 0.02
• Frequency of dominant allele, F (p) = 1 - q = 1 - 0.02 = 0.98

2) If 14% of individuals in a population have the recessive phenotype (aa), what percentage of the population is heterozygous ?

• Frequency of recessive genotype (aa or q²) = 14% = 14/100 = 0.14
• Frequency of recessive allele (q) = sqrt(0.14) = 0.3742
• Frequency of dominant allele (p) = 1 - q = 1 - 0.3742 = 0.6258
• Frequency of heterozygotes = 2*p*q = 2*0.6258*0.3742 = 0.4683