What are the four nitrogenous bases found in RNA? a. cytosine, guanine, thymine, uracil (C, G, T, U) b. adenine, cytosine, guanine, thymine (A, C, G, T) c. adenine, cytosine, guanine, uracil (A, C, G, U) d. alanine, cysteine, glycine, threonine (A, C, G, T)
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The Hardy-Weinberg Principle
Problem 12Taylor, Simon, Dickey, Hogan - 10th Edition
Textbook Question
Sickle-cell disease is caused by a recessive allele. Roughly one out of every 400 African Americans (0.25%) is afflicted with sickle-cell disease. Use the Hardy-Weinberg equation to calculate the percentage of African Americans who are carriers of the sickle-cell allele. (Hint: q2 = 0.0025.)
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1
Identify the given value in the problem, which is the frequency of individuals with sickle-cell disease (q^2 = 0.0025).
Calculate the frequency of the sickle-cell allele (q) by taking the square root of q^2. Use the formula q = \sqrt{q^2}.
Use the Hardy-Weinberg equilibrium principle which states that p + q = 1, where p is the frequency of the normal allele. Calculate p by rearranging the formula to p = 1 - q.
Determine the frequency of carriers (2pq) using the Hardy-Weinberg equation for heterozygotes. Substitute the values of p and q into the formula 2pq.
Convert the decimal result of 2pq into a percentage by multiplying by 100 to find the percentage of African Americans who are carriers of the sickle-cell allele.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Sickle-Cell Disease and Alleles
Sickle-cell disease is a genetic disorder caused by a mutation in the hemoglobin gene, resulting in abnormal hemoglobin that distorts red blood cells into a sickle shape. This condition is inherited in a recessive manner, meaning an individual must have two copies of the sickle-cell allele to exhibit the disease. Understanding the genetic basis of sickle-cell disease is crucial for applying the Hardy-Weinberg principle.
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Genes & Alleles
Hardy-Weinberg Principle
The Hardy-Weinberg principle is a fundamental concept in population genetics that describes how allele and genotype frequencies remain constant from generation to generation in a large, randomly mating population, provided that certain conditions are met. The equation p² + 2pq + q² = 1 allows for the calculation of allele frequencies, where p is the frequency of the dominant allele and q is the frequency of the recessive allele. This principle is essential for determining carrier frequencies in populations.
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The Hardy-Weinberg Principle Example 1
Carrier Frequency Calculation
In the context of genetic disorders, a carrier is an individual who possesses one copy of a recessive allele but does not exhibit the disease phenotype. The carrier frequency can be calculated using the Hardy-Weinberg equation, specifically the term 2pq, where q represents the frequency of the recessive allele. By knowing the prevalence of the disease (q²), one can derive q and subsequently calculate the percentage of carriers in the population.
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A. Calculating Genotype Frequency from Allele Frequency
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