Ch. 20 - Population Genetics and Evolution at the Population, Species, and Molecular Levels

Sanders - Genetic Analysis: An Integrated Approach 3rd Edition

Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172당신이 사용하는 게 아니라요?교과서 변경

Sanders 3rd Edition

Ch. 20 - Population Genetics and Evolution at the Population, Species, and Molecular Levels

문제 19b

20장, 문제 19b

Sickle cell disease (SCD) is found in numerous populations whose ancestral homes are in the malaria belt of Africa and Asia. SCD is an autosomal recessive disorder that results from homozygosity for a mutant β-globin gene allele. Data on one affected population indicates that approximately 8 in 100 newborn infants have SCD.
What is the frequency of carriers of SCD in the population?

검증된 단계별 안내

Step 1: Recognize that this problem involves Hardy-Weinberg equilibrium, which is used to calculate allele and genotype frequencies in a population. The equation is p² + 2pq + q² = 1, where p and q are the frequencies of the dominant and recessive alleles, respectively.

Step 2: Identify the given information. The problem states that 8 in 100 newborns have SCD, which corresponds to the homozygous recessive genotype (q²). Thus, q² = 0.08.

Step 3: Calculate the frequency of the recessive allele (q) by taking the square root of q². Use the formula q = √q².

Step 4: Determine the frequency of the dominant allele (p) using the relationship p + q = 1. Rearrange the equation to solve for p: p = 1 - q.

Step 5: Calculate the frequency of carriers (heterozygotes) using the Hardy-Weinberg formula for heterozygotes: 2pq. Multiply 2 by the frequency of p and the frequency of q to find the carrier frequency.

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이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.

영상 길이:

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Autosomal Recessive Inheritance

Autosomal recessive inheritance refers to a pattern where two copies of a mutated gene (one from each parent) are necessary for an individual to express a genetic disorder. In the case of sickle cell disease (SCD), individuals who are homozygous for the mutant β-globin gene allele exhibit the disease, while heterozygous individuals (carriers) do not show symptoms but can pass the allele to their offspring.

Hardy-Weinberg Principle

The Hardy-Weinberg principle provides a mathematical framework for understanding genetic variation in a population at equilibrium. It states that allele and genotype frequencies will remain constant from generation to generation in the absence of evolutionary influences. This principle can be used to estimate carrier frequencies in populations by applying the equations p² + 2pq + q² = 1, where p and q represent the frequencies of the dominant and recessive alleles, respectively.

Carrier Frequency Calculation

Carrier frequency refers to the proportion of individuals in a population who carry one copy of a recessive allele for a genetic disorder. To calculate the carrier frequency for SCD, one can use the prevalence of the disease (homozygous individuals) to determine the frequency of the recessive allele (q) and then apply the formula 2pq to find the frequency of carriers (heterozygous individuals), where p is the frequency of the dominant allele.

관련 실천

교과서 질문

The frequency of tasters and nontasters of PTC varies among populations. In population A, 64% of people are tasters (an autosomal dominant trait) and 36% are nontasters. In population B, tasters are 75% and nontasters 25%. In population C, tasters are 91% and nontasters are 9%.

Calculate the frequency of the dominant (T) allele for PTC tasting and the recessive (t) allele for nontasting in each population.

742

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교과서 질문

Epidemiologic data on the population in the previous problem reveal that before the application of modern medical treatment, natural selection played a major role in shaping the frequencies of alleles. Heterozygous individuals have the highest relative fitness, and in comparison with heterozygotes, those who are βᴬβᴬ have a relative fitness of 82%, but only about 32% of those with SCD survived to reproduce. What are the estimated equilibrium frequencies of βᴬ and βˢ in this population?

398

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교과서 질문

Genetic Analysis 20.1 predicts the number of individuals expected to have the blood group genotypes MM, MN, and NN. Perform a chi-square analysis using the number of people observed and expected in each blood-type category, and state whether the sample is in H-W equilibrium.

532

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교과서 질문

Assuming that Hardy–Weinberg conditions apply, determine the genotype frequencies in each population.

1290

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교과서 질문

In a population of rabbits, f(C₁) = 0.70 and f(C₂) = 0.30. The alleles exhibit an incomplete dominance relationship in which C₁C₁ produces black rabbits, C₁C₂ produces tan-colored rabbits, and C₂C₂ produces rabbits with white fur. If the assumptions of the Hardy–Weinberg principle apply to the rabbit population, what are the expected frequencies of black, tan, and white rabbits?

851

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교과서 질문

Sickle cell disease (SCD) is found in numerous populations whose ancestral homes are in the malaria belt of Africa and Asia. SCD is an autosomal recessive disorder that results from homozygosity for a mutant β-globin gene allele. Data on one affected population indicates that approximately 8 in 100 newborn infants have SCD.

What are the frequencies of the wild-type (βᴬ) and mutant (βˢ) alleles in this population?

574

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