Question

In the Hardy-Weinberg equation, what portion represents the frequency of individuals that do not exhibit a recessive disease but are carriers of a recessive allele? a. \(q\) b. \(p^{2}\) c. \(2 p q\) d. \(q^{2}\) e. both b and d

Short answer

The frequency of individuals that are carriers of a recessive allele but do not exhibit the recessive disease are represented by \(2pq\). Hence, the correct answer is c. \(2pq\).

Step-by-step solution

Identifying the terms

We first identify what the terms in the Hardy-Weinberg equation represent: \(p^{2}\) represents the frequency of homozygous dominant individuals, \(2pq\) represents the frequency of heterozygous individuals, and \(q^{2}\) represents the frequency of homozygous recessive individuals. The values of p and q represent the frequencies of the dominant and recessive alleles respectively.

Identifying the carriers of a recessive allele

Next, we need to identify the carriers of a recessive allele. These would be individuals that have one copy of the recessive allele, but do not exhibit the recessive trait. This is because they also have a dominant allele which masks the effect of the recessive allele. So these individuals are the heterozygous individuals.

Choose the correct answer

Based on our understanding of what each term in the Hardy-Weinberg equation represents, the carriers of a recessive allele are represented by term \(2pq\).

Key concepts

Heterozygous Individuals

Exploring the concept of heterozygous individuals helps us understand the genetic variety within a population. In genetics, heterozygosity refers to the presence of two different alleles at a particular gene locus on a chromosome. For a given trait determined by a single gene locus, an individual with two different alleles is considered heterozygous for that trait. This genetic composition is significant in the Hardy-Weinberg equation, which is used to calculate the frequencies of different genotypes in a population.

In the context of the Hardy-Weinberg principle, which serves as a model for evaluating genetic equilibrium, the term '2pq' is particularly important. It represents the proportion of heterozygous individuals within a population. These individuals carry one dominant allele, denoted as 'p', and one recessive allele, denoted as 'q'. The interplay between these alleles in a heterozygous individual results in the expression of the dominant trait, with the recessive trait being hidden, yet still present in the carriers' genetic information.

Significance of Heterozygosity in Populations

Genetic diversity, which includes the proportion of heterozygous individuals, is vital for the adaptability and survival of a population. This diversity allows for a range of phenotypes that can withstand various environmental pressures. High heterozygosity is often associated with greater resilience to changing conditions and a reduced chance of inheriting detrimental recessive traits.

Recessive Allele Carriers

Recessive allele carriers are individuals who have one copy of a recessive allele for a particular trait or disease. In these carriers, the recessive allele is 'masked' by the presence of a dominant allele. Hence, while they do not display the trait associated with the recessive allele, they can pass it on to their offspring.

Returning to the Hardy-Weinberg equation, the term '2pq' corresponds to these carriers. An essential point to grasp is that even though these individuals do not exhibit the recessive trait, they are vital in figuring out how a trait can emerge in a population and in understanding the genetic risks present within a family or community.

Carrier Detection and Genetic Counseling

Identifying carriers of recessive alleles is an important aspect of genetic counseling, especially for couples planning to have children. If both parents are carriers of the same recessive trait, represented by '2pq' for each, their offspring have a possibility, specifically a 25% chance if we consider Hardy-Weinberg equilibrium, of being homozygous recessive ('qq') and, therefore, expressing the recessive phenotype.

Allele Frequencies

Allele frequencies refer to how common certain alleles of a gene are within a population. They provide an understanding of the genetic variation and are denoted by 'p' and 'q' in the Hardy-Weinberg equation, where 'p' is the frequency of the dominant allele, and 'q' is the frequency of the recessive allele.

In a stable population that meets certain criteria (no mutation, random mating, no natural selection, large population size, and no migration), the allele frequencies are expected to remain constant from generation to generation, according to the Hardy-Weinberg principle. It's vital to note that 'p' and 'q' must sum to 1 since they represent all the possible alleles at a given locus in the population.

Calculating Allele Frequencies

To calculate allele frequencies from genotype frequencies, one can use the observed numbers of homozygous dominant ('pp'), homozygous recessive ('qq'), and heterozygous individuals ('pq') within a population. Understanding these frequencies is crucial for predicting the likelihood of particular traits being passed on and for making inferences about population health, potential genetic diseases, and evolution.