Study Guide for Campbell Biology
11th Edition
ISBN: 9780134443775
Author: Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Jane B. Reece, Martha R. Taylor, Michael A. Pollock
Publisher: PEARSON
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Textbook Question
Chapter 23, Problem 6IQ
Why hasn’t the highly deleterious sickle-cell allele been selected against and eliminated from the gene pool of the U.S. population?
Why is this allele at such a relatively high frequency in the gene pool of some African populations?
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In parts of equatorial Africa, where the malaria parasite is most common, the sickle-cell allele constitutes 20% of the ß-hemoglobin alleles in the human gene pool. The sickle cell trait provides an advantage against
malaria compared to people with normal hemoglobin. In the United States, the parasite that causes malaria is not present, but African Americans whose ancestors were from equatorial Africa have the sickle-cell B-
hemoglobin allele. These differences in traits illustrate
O inclusive fitness because people have evolved molecular differences to adapt to environmental stimuli
O inclusive fitness because ß-hemoglobin increases the proliferation of beneficial traits in the population
O relative fitness because people have evolved molecular differences to an environmental pathogen
O relative fitness because the molecular differences in ß-hemoglobin are passed to the next generation
Sickle cell anemia is caused by a recessive allele at a single gene. As we discussed in class, being a homozygote for the sickle cell allele is almost always lethal, but heterozygotes tend to be resistant against malaria although they have a mild form of anemia. Because of this heterozygote advantage, the allele for sickle cell anemia has a frequency of more than 10% in some human populations.
How would present allele frequencies of the sickle cell allele change, if there was no heterozygote advantage or disadvantage (that is, that heterozygotes would be identical to ‘normal’ homozygotes – no malaria resistance, no anemia)? How would the change in sickle cell allele frequencies compare to scenario a (extirpation of malaria)
The allele for sickle anemia is found at higher frequencies in central Africa than in other parts of the world. What are the advantage and disadvantages?
Chapter 23 Solutions
Study Guide for Campbell Biology
Ch. 23 - a. What is a major source of genetic variation for...Ch. 23 - In a population of 200 mice, 98 are homozygous...Ch. 23 - Use the allele frequencies you determined in...Ch. 23 - Practice using the Hardy-Weinberg equation so that...Ch. 23 - Prob. 5IQCh. 23 - Why hasnt the highly deleterious sickle-cell...Ch. 23 - a. What is Hardy-Weinberg equilibrium? b. Define...Ch. 23 - Prob. 2SYKCh. 23 - Prob. 1TYKCh. 23 - Prob. 2TYK
Ch. 23 - Prob. 3TYKCh. 23 - Prob. 4TYKCh. 23 - Mice have an estimated 1,000 olfactory receptor...Ch. 23 - Prob. 6TYKCh. 23 - If a population has the following genotype...Ch. 23 - In a population with two alleles, B and b, the...Ch. 23 - Prob. 9TYKCh. 23 - Prob. 10TYKCh. 23 - In a random sample of a population of shorthorn...Ch. 23 - Genetic drift is likely to be seen in a population...Ch. 23 - Porphyria variegata is a genetic disease...Ch. 23 - Cystic fibrosis is a very serious genetic disorder...Ch. 23 - Prob. 15TYKCh. 23 - Prob. 16TYKCh. 23 - Prob. 17TYKCh. 23 - Prob. 18TYKCh. 23 - Prob. 19TYKCh. 23 - Prob. 20TYKCh. 23 - Prob. 21TYK
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- Tay-Sachs disease is a recessive genetic disease. Individuals with this disease rarely survive past the age of four. In the general population, approximately 1 person in 300 carries the allele for this disease. However, in some populations, including the Irish Americans, the Ashkenazi Jews, and the Cajuns from Louisiana, the proportion of Tay-Sachs carriers is much higher (1 in 27 to 1 in 50) than in other populations. Such high frequency of an otherwise rare allele is expected when Question 24 options: populations experienced disruptive selection populations were founded by a small number of settlers the allele is advantageous at the heterozygous state populations have higher than average mutation rates populations experienced stabilizing selectionarrow_forwardSteven Frank and Laurence Hurst argued that a cytoplasmically inherited mutation in humans that has severe effects in males but no effect in females will not be eliminated from a population by natural selection because only females pass on mtDNA. Using this argument, explain why males with Leber hereditary optic neuropathy are more severely affected than females.arrow_forwardNieman-Pick Syndrome involves a defective enzyme, sphyngomylinase. It is usually fatal before the age of 3. The defective allele frequency is 0.01 in Ashkenazi populations. Let’s call the healthy allele A, and the lethal allele a. a) What is the frequency of allele A? Assuming Hardy-Weinberg equilibrium, how many people do you expect to have the three genotypes in a population of 10,000? b) AA:_______ c) Aa:________ d) aa:_________arrow_forward
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- The allele of the gene responsible for the lung disorder, cystic fibrosis rose to prominence in Europe in the 1800s. Cystic fibrosis disease results from thick mucus accumulating in the lungs, which occurs in individuals who are homozygous for the CF allele. A pleiotropic effect is that heterozygous individuals are less likely to suffer from diarrhea. During the European cholera epidemics of the 1800s, resistance against diarrhea conferred a survival advantage such that approximately one in every 400 people in some European populations have cystic fibrosis. Fill in the table below with the genotype and allele frequencies for this 1 in 400 occurrence and provide the Hardy-Weinberg principle model you will be using. (Assume that individuals with the cystic fibrosis trait (CF) reproduce normally and that good sanitation means that there is currently no fitness advantage to diarrhea resistance.) phenotype CF DR normal (totals) Genotype cc Cc CC Number of Individuals 1 ______…arrow_forwardWhy do recessive lethals persist in a population? Provide an example of a recessive lethal allele.arrow_forwardExplain the High frequency of the sickle-cell allele HbβS in regions of Africa where malaria is prevalent?arrow_forward
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