Question

In a population where only the total number of individuals wit the dominant phenotype is known, how can you calculate th percentage of carriers and homozygous recessives?

Short answer

Question: In a population of 100 individuals, 75 have the dominant phenotype. Calculate the percentage of carriers (heterozygous) and homozygous recessive individuals in the population. Answer: In this population, 25% are homozygous recessive individuals and 75% are carriers (heterozygous).

Step-by-step solution

Understanding the Basis of Problem

First, we need to understand the principles of Mendelian genetics and the concept of dominant and recessive alleles. In a diploid organism, like humans, each individual has two copies of each gene. They can either have two dominant alleles (homozygous dominant), two recessive alleles (homozygous recessive), or one of each (heterozygous). The dominant allele will be expressed in both homozygous dominant and heterozygous individuals, while the recessive allele will only be expressed in homozygous recessive individuals. We are given the total number of individuals with the dominant phenotype, which includes both homozygous dominant and heterozygous individuals. We are required to calculate the percentage of carriers (heterozygous) and homozygous recessives in the population.

Using Given Information to Calculate Ratio

Suppose there are 'T' individuals in the population, and 'D' individuals have the dominant phenotype (heterozygous and homozygous dominant). Let ‘H’ be the number of heterozygous (carriers) and ‘S’ be the number of homozygous recessive individuals. Then, we can write the following equation: D = T - S Here, we can see that if we have the value of 'D' and 'T', we can calculate the number of homozygous recessive individuals (S).

Calculate the Percentage of Carriers and Homozygous Recessives

To calculate the percentage of carriers (heterozygous) and homozygous recessives, we can use the following formulas: Percentage of Homozygous Recessives = (S/T) x 100% Percentage of Carriers (Heterozygous) = 100% - Percentage of Homozygous Recessives We can use these formulas to find the percentages after calculating the value of 'S' (Homozygous recessive) from Step 2. For example, let's assume there are 100 individuals in the population (T = 100) and 75 individuals have the dominant phenotype (D = 75). From Step 2, we can calculate S as: S = T - D = 100 - 75 = 25 Now, we can calculate the percentage of homozygous recessives and carriers using the formulas from Step 3: Percentage of Homozygous Recessives = (25/100) x 100% = 25% Percentage of Carriers (Heterozygous) = 100% - 25% = 75% So, in this example, 25% of the population are homozygous recessives and 75% are carriers (heterozygous).