Question

Left Foot Syndrome is a rare condition in which individuals are born with two left feet if they are homozygous for a recessive r allele (w) genotype, those who are heterozygous (Rr) and homorygous (RR) are born with correct set of feet one right foot and one left foot. However because people wear shoes, the actual number of double left foot people are not known. Last year, there were 38,972 deaths in the population and of those 117 individuals were visibly identified as left footed individuals Assuming the deaths were random and hence representative of the general population The total population is nearly a million (1,000,067) individuals. Using the data from the death counts, determine: Aj the gene frequencies in the death sample and B) genotype frequencies of the death sample. I C) the death rate of the population D) the proportion of the total population that are: i) Hidden double left foots ii) Heterozygous right footed individuals ii) Homozygous right footed individuals

Answer 1

Total population = 1000067

Total number of deaths last year= 38972

Among 38972 dead population,117 were left footed.

A.) Total population in death sample= 38972

Left footed individuals are homozygous recessive, so their genotype is rr

So genotype frequency of rr = 117/38972= 0.003 =q²

So,q = 0.054

We know, p+q =1

So p= 1-q =0.946

Therefore,gene frequencies of the death sample, p =0.946 and q= 0.054

B.) Left footed individuals are homozygous recessive, so their genotype is rr

So genotype frequency of rr = 117/38972= 0.003 =q²

So the rest of the population in the sample are visibly normal individuals,that is they are either heterozygous or homozygous dominant for the syndrome.

38855 individuals are either heterozygous (Rr) or homozygous dominant (RR) for the syndrome.

Genotype frequency of heterozygous (Rr) = 2pq= 2 X0.946 X0.054=0.102

Genotype frequency of homozygous dominant(RR) = p² =0.946 X 0.946= 0.894

C.) The death rate of the population is = Number of deaths in a year /Total population = 38972/ 1000067 =0.039

D.)i) Proportion of total population that are hidden double foots= 117/ 1000067=0.00012

This the homozygous recessive frequency in the total population= q²

So, q= 0.0109

We know, p+q=1

So, p =0.9891

ii) Heterozygous right footed individual proportion= 2pq = 0.022

iii) Homozygous right footed individual proportion=p² = 0.978