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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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)
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
Why does sickle-cell anaemia persist in the human population when it is believed that the harmful alleles get eliminated from the population after a certain time?
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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