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 19a

20장, 문제 19a

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?

검증된 단계별 안내

Understand the problem: Sickle cell disease (SCD) is an autosomal recessive disorder, meaning individuals with the disease are homozygous for the mutant allele (βˢβˢ). The problem provides the frequency of affected individuals in the population (q² = 8/100 = 0.08) and asks for the allele frequencies of the wild-type (βᴬ) and mutant (βˢ) alleles.

Recall the Hardy-Weinberg principle: The Hardy-Weinberg equation is p² + 2pq + q² = 1, where p is the frequency of the wild-type allele (βᴬ), q is the frequency of the mutant allele (βˢ), p² represents the frequency of homozygous wild-type individuals, 2pq represents the frequency of heterozygous carriers, and q² represents the frequency of homozygous mutant individuals.

Determine the frequency of the mutant allele (q): Since q² = 0.08, take the square root of q² to find q. Mathematically, q = √(0.08).

Calculate the frequency of the wild-type allele (p): Using the relationship p + q = 1, solve for p by subtracting q from 1. Mathematically, p = 1 - q.

Summarize the allele frequencies: The frequency of the wild-type allele (βᴬ) is p, and the frequency of the mutant allele (βˢ) is q. These values represent the proportion of each allele in the population.

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주요 개념

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

Autosomal Recessive Inheritance

Autosomal recessive inheritance means that a trait or disorder is expressed only when an individual has two copies of the recessive allele, one from each parent. In the case of sickle cell disease (SCD), individuals must be homozygous for the mutant β-globin gene allele (βˢ) to exhibit the disease. Carriers, who have one wild-type allele (βᴬ) and one mutant allele (βˢ), do not show symptoms but can pass the mutant allele to their offspring.

Hardy-Weinberg Principle

The Hardy-Weinberg principle provides a mathematical framework for understanding allele frequencies in a population at equilibrium. It states that the frequencies of alleles and genotypes will remain constant from generation to generation in the absence of evolutionary influences. This principle can be used to calculate the frequencies of the wild-type (βᴬ) and mutant (βˢ) alleles in the population based on the prevalence of the disease.

Allele Frequency Calculation

Allele frequency refers to how often a particular allele appears in a population. For a recessive disorder like SCD, if the prevalence of the disease is known, the frequency of the mutant allele can be calculated using the formula p² + 2pq + q² = 1, where q² represents the frequency of the homozygous recessive genotype. From this, the frequencies of both the mutant (q) and wild-type (p) alleles can be derived, allowing for a better understanding of genetic diversity in the population.

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.

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교과서 질문

Certain animal species, such as the black-footed ferret, are nearly extinct and currently exist only in captive populations. Other species, such as the panda, are also threatened but exist in the wild thanks to intensive captive breeding programs. What strategies would you suggest in the case of black-footed ferrets and in the case of pandas to monitor and minimize inbreeding depression?

580

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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?

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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.

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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 is the frequency of carriers of SCD in the population?

681

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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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