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 10c

20장, 문제 10c

The ability to taste the bitter compound phenylthiocarbamide (PTC) is an autosomal dominant trait. The inability to taste PTC is a recessive condition. In a sample of 500 people, 360 have the ability to taste PTC and 140 do not. Calculate the frequency of each genotype.

검증된 단계별 안내

Step 1: Define the alleles and genotypes. Let 'T' represent the dominant allele for the ability to taste PTC, and 't' represent the recessive allele for the inability to taste PTC. The genotypes are TT (homozygous dominant), Tt (heterozygous), and tt (homozygous recessive).

Step 2: Use the Hardy-Weinberg principle to model the population. The Hardy-Weinberg equation is p² + 2pq + q² = 1, where p is the frequency of the dominant allele (T), q is the frequency of the recessive allele (t), p² represents the frequency of TT, 2pq represents the frequency of Tt, and q² represents the frequency of tt.

Step 3: Calculate q², the frequency of the homozygous recessive genotype (tt). Since 140 out of 500 people cannot taste PTC, the frequency of the recessive phenotype is 140/500 = 0.28. This is equal to q².

Step 4: Solve for q, the frequency of the recessive allele. Take the square root of q² to find q. Use the equation q = √(q²).

Step 5: Calculate p, the frequency of the dominant allele. Use the relationship p + q = 1 to solve for p. Then, calculate the frequencies of each genotype: p² for TT, 2pq for Tt, and q² for tt. These represent the proportions of the population with each genotype.

비슷한 문제에 대한 검증된 영상 답변:

이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.

영상 길이:

도움이 되었나요?

주요 개념

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

Autosomal Dominance and Recessiveness

In genetics, traits can be classified as dominant or recessive based on how they are expressed in an organism. An autosomal dominant trait, like the ability to taste PTC, requires only one copy of the dominant allele for expression, while a recessive trait requires two copies of the recessive allele. This distinction is crucial for understanding inheritance patterns and predicting genotype frequencies in a population.

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 is essential for calculating genotype frequencies based on observed phenotypic ratios, as it allows for predictions about genetic diversity.

Genotype Frequency Calculation

Genotype frequency refers to the proportion of different genotypes in a population. To calculate these frequencies, one can use the observed phenotypic data along with the principles of inheritance. For the PTC tasting trait, knowing the number of tasters and non-tasters allows for the application of the Hardy-Weinberg equations to derive the frequencies of the homozygous dominant, heterozygous, and homozygous recessive genotypes.

관련 실천

교과서 질문

Biologists have proposed that the use of antibiotics to treat human infectious disease has played a role in the evolution of widespread antibiotic resistance in several bacterial species, including Staphylococcus aureus and the bacteria causing gonorrhea, tuberculosis, and other infectious diseases. Explain how the evolutionary mechanisms mutation and natural selection may have contributed to the development of antibiotic resistance.

487

views

교과서 질문

In Island Melanesia and Polynesia, most mtDNA haplotypes are of Asian ancestry, whereas Y chromosome haplotypes are predominantly New Guinean. Provide a hypothesis for this sex-biased distribution.

449

views

교과서 질문

The ability to taste the bitter compound phenylthiocarbamide (PTC) is an autosomal dominant trait. The inability to taste PTC is a recessive condition. In a sample of 500 people, 360 have the ability to taste PTC and 140 do not. Calculate the frequency of the recessive allele.

563

views

교과서 질문

The figure illustrates the effect of an ethanol-rich and an ethanol-free environment on the frequency of the Drosophila Adh^F allele in four populations in a 50-generation laboratory experiment. Population 1 and population 2 were reared for 50 generations in a high-ethanol environment, while control 1 and control 2 populations were reared for 50 generations in a zero-ethanol environment. Describe the effect of each environment on the populations, and state any conclusions you can reach about the role of any of the evolutionary processes in producing these effects.

498

views

교과서 질문

Denisovans are known from bones found in Denisova Cave in the Altai Mountains in Siberia, but traces of their DNA are found in Australians and Melanesians, whose ancestors likely migrated across Asia much farther to the south. How can these geographic differences be reconciled?