Need help answering 3 questions on genetics.
Exercise 1 Exercise 1A (Hardy-Weinberg) Note: These questions require a basic knowledge of classical genetics, as covered in the prerequisite course BIOL 204. General hints to solve Hardy-Weinberg (HW) questions: A . Ensure that all Hardy-Weinberg conditions are met. If they aren’t, the formulas will not work. In some instances, application of the Hardy-Weinberg equations might reveal contradictions, from which you can conclude that HW conditions were not met in the first place. B . Populations can only be understood by studying a combination of two different levels: · the genotypes, which represent individuals (e.g., Aa represents an individual). The formula p² + 2pq + q² = 1 refers to those genotype frequencies. · the alleles, an abstract concept that represents the gene pool, represented by allele frequencies: p + q = 1.
By convention, the dominant allele frequency refers to p, the recessive one to q. In most cases, the question will reveal one of the parameters (e.g., p), and the rest is a series of simple calculations. If you know that a population exists under HW conditions, you won’t have to rearrange the main formula. For example, if you are looking for the genotype frequency of the dominant allele, you can simply calculate the square of the dominant allele frequency: p² = p · p. C . In addition to applying the HW formulas, you will be required to translate frequencies into numbers of individuals (or vice versa). For example, a population of 800 individuals with a particular genotype frequency of 65% will comprise 800 × 0.65 = 520 individuals. D . Here we will only use the simplified conditions of two alleles on one locus. Multiple alleles and alleles on more than one locus would require extensions of the HW formula that we don’t cover in this course. E . When writing down the answers, you must include all steps that it took you to get to the solution. Just writing down the correct end results will incur significant mark deductions. F . In the calculations, numbers may be rounded to four decimal digits if required. For example, 2.78318 may be rounded to 2.7832. Q 1. In Drosophila, the allele for grey body colour is dominant over the one for black bodies; both alleles are on the same locus. In a population where we assume Hardy-Weinberg conditions, 80% of the flies are grey. In a population of 6500 flies, what is the total number of flies that are both homozygous and grey? Write down all required steps. Q 2. In a large population of rats, fur colour is determined by a single gene with two different alleles. The dominant allele causes a brown fur colour, while white rats are a result of the recessive allele. We assume HW conditions. A study revealed that only 1% of the gene pool has the recessive allele. What percentage of brown rats would you expect in the population? Write down all steps. Q 3. Cystic fibrosis is a recessive genetic disease that affects approximately one human baby out of every 2500 in the European Union population. Its symptoms involve excessive mucus production in the lungs, and life expectancy for these patients is drastically reduced. We assume Hardy-Weinberg conditions. What is the frequency of the dominant genotype? Write down all steps. What is the frequency of the recessive allele? Write down all steps. Assuming the same disease frequency as in the general EU population, how many carrier individuals (carriers have the heterozygous genotype without showing the symptoms) would you find in the population of Sweden (total population 10 million people)? Write down all steps.