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

Sanders - Genetic Analysis: An Integrated Approach 3rd Edition

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Sanders 3rd Edition

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

문제 31d

20장, 문제 31d

Albinism, an autosomal recessive trait characterized by an absence of skin pigmentation, is found in 1 in 4000 people in populations at equilibrium. Brachydactyly, an autosomal dominant trait producing shortened fingers and toes, is found in 1 in 6000 people in populations at equilibrium. For each of these traits, calculate the frequency of For albinism only, what is the frequency of mating between heterozygotes?

검증된 단계별 안내

Step 1: Understand the inheritance pattern of albinism. Albinism is an autosomal recessive trait, meaning that an individual must inherit two copies of the recessive allele (aa) to express the trait. Heterozygotes (Aa) are carriers but do not exhibit the phenotype.

Step 2: Use the Hardy-Weinberg equilibrium to calculate allele frequencies. The Hardy-Weinberg equation is p² + 2pq + q² = 1, where p is the frequency of the dominant allele (A), q is the frequency of the recessive allele (a), p² represents the frequency of homozygous dominant individuals (AA), 2pq represents the frequency of heterozygotes (Aa), and q² represents the frequency of homozygous recessive individuals (aa).

Step 3: Since the frequency of albinism (aa) is given as 1 in 4000, this corresponds to q² = 1/4000. Solve for q, the frequency of the recessive allele, by taking the square root of q².

Step 4: Once q is determined, calculate p, the frequency of the dominant allele, using the relationship p + q = 1. Rearrange to find p = 1 - q.

Step 5: To find the frequency of mating between heterozygotes, calculate the probability of two heterozygotes (2pq) mating. This is done by squaring the heterozygote frequency (2pq) to represent the probability of two heterozygotes mating in the population.

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주요 개념

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Autosomal Recessive Inheritance

Autosomal recessive inheritance occurs when a trait is expressed only when an individual has two copies of the recessive allele. In the case of albinism, individuals must inherit the recessive allele from both parents to exhibit the trait. This concept is crucial for understanding how the frequency of the trait in a population can be calculated using the Hardy-Weinberg principle.

Hardy-Weinberg Equilibrium

The Hardy-Weinberg equilibrium is a principle that describes the genetic variation in a population that is not evolving. It provides a mathematical framework to calculate allele and genotype frequencies based on assumptions such as random mating and no selection. This principle is essential for determining the frequency of alleles in a population, which can be applied to calculate the mating frequency of heterozygotes for traits like albinism.

Heterozygote Frequency

Heterozygote frequency refers to the proportion of individuals in a population that carry two different alleles for a given gene. In the context of albinism, calculating the frequency of mating between heterozygotes involves determining how often individuals with one dominant and one recessive allele (carriers) mate with each other. This frequency can be derived from the allele frequencies established through the Hardy-Weinberg equations.