Midphalangeal hair (hair on top of the middle segment of the fingers) is a commo
ID: 48173 • Letter: M
Question
Midphalangeal hair (hair on top of the middle segment of the fingers) is a common phenotype caused by a dominant allele, M. Homozygotes for the recessive allele, mm, lack hair on the middle segment of their fingers. In a particular group of families in which both parents had midphalangeal hair (M--), 1853 of their children showed midphalangeal hair, whereas 209 children did not.
a)Find the approximate proportion of the children who had two heterozygous parents.
b)What are all the other parental genotypic combinations that gave rise to the other children?
Explanation / Answer
The children born were some are with the midphalangeal and others are without that condition. So the genotype of the parents may be MMxMM and MmxMm.
In this 209 children are lack of that condition so the ratio of the heterozygous parents offsprings may be 1:3 ( Without condition to with).
The total children born were 1853+209=2062 children. Out of that 209 are lack of the condition and 209x3=627 children are with heterozygote parents.
a) So 209+627=836 children are with heterozygous parents. The approximate proportion is 836/2062=0.40
b) The other genotypic conditions may be MMxMM, MMxMm.