Human Heredity: Principles and Issues (MindTap Course List)
11th Edition
ISBN: 9781305251052
Author: Michael Cummings
Publisher: Cengage Learning
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Textbook Question
Chapter 19, Problem 2CS
If allele frequencies in the hemoglobin gene are influenced by sickle cell anemia on the one hand and by resistance to malaria on the other hand, what factors may cause a change in these allele frequencies over time?
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In a region of Africa, where malaria is prevalent, 40% of the population are found to have sickle-cell anemia. The disease is caused by an abnormal hemoglobin that is found in both homozygotes (S2S2) and heterozygotes (S1S2). Many homozygotes (S2S2) suffer from anemia and often die. Heterozygotes (S1S2) incur a much less debilitating malady called "sickling trait". Approximately 3% of the people with abnormal hemoglobin are homozygotes (1.2\% of the entire population). The fitness of the S2S2 homozygotes is only 1/4 that of the heterozygotes. Where malaria is prevalent, heterozygotes exhibit overdominance with respect to fitness. How would you calculate relative fitness of the S1S1 homozygotes if you're assuming the population is at an equilibrium frequency for S2?
Chapter 19 Solutions
Human Heredity: Principles and Issues (MindTap Course List)
Ch. 19.8 - Why dont genetic markers on the Y chromosome...Ch. 19.8 - Prob. 2GRCh. 19 - If you suspected that heterozygous carriers of a...Ch. 19 - If allele frequencies in the hemoglobin gene are...Ch. 19 - Prob. 1QPCh. 19 - How Can We Measure Allele Frequencies in...Ch. 19 - How Can We Measure Allele Frequencies in...Ch. 19 - Prob. 4QPCh. 19 - Prob. 5QPCh. 19 - How Can We Measure Allele Frequencies in...
Ch. 19 - How Can We Measure Allele Frequencies in...Ch. 19 - How Can We Measure Allele Frequencies in...Ch. 19 - Using the HardyWeinberg Law in Human Genetics...Ch. 19 - Prob. 10QPCh. 19 - Using the HardyWeinberg Law in Human Genetics In a...Ch. 19 - Prob. 12QPCh. 19 - Measuring Genetic Diversity in Human Populations...Ch. 19 - Measuring Genetic Diversity in Human Populations...Ch. 19 - Prob. 15QPCh. 19 - Measuring Genetic Diversity in Human Populations...Ch. 19 - Prob. 17QPCh. 19 - Prob. 18QPCh. 19 - Measuring Genetic Diversity in Human Populations...Ch. 19 - Natural Selection Affects the Frequency of Genetic...Ch. 19 - Prob. 21QPCh. 19 - Prob. 22QPCh. 19 - The Evolutionary History and Spread of Our Species...Ch. 19 - Prob. 24QPCh. 19 - Genomics and Human Evolution The Denisovan genome...
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- Sickle-cell disease (often called sickle-cell anemia) is a disease that is caused by a mutation to the gene that is responsible for producing the protein hemoglobin. Remember that hemoglobin is a protein in the red blood cells which is responsible for carrying oxygen throughout the body. When a person possesses the mutated hemoglobin allele, their red blood cells take on an altered shape and this results in a variety of symptoms ranging from general weakening of the body, damage to the organs and even death. The sickle cell allele is recessive to the healthy allele, thus only individuals that are homozygous for the recessive allele will have sickle-cell disease. Individuals that are homozygous for the healthy allele, along with heterozygous, individuals will be physically healthy. Question: Given that this mutated allele will cause disease and death in individuals, what would you predict to occur to the frequency of this allele in the population? Explain.arrow_forwardGiven the information regarding sickle cell anemia, if two carriers were to have children, what would be the genotypes and phenotypes of their children? Would any of the children show symptoms of the disease?arrow_forwardSickle cell anemia follows a single-gene pattern of inheritance, with two alleles: one allele (S) produces normal hemoglobin, and the other (s) produces abnormal hemoglobin. Describe the phenotype outcome for each of the three possible genotypes (SS, Ss and ss), with regard to sickle cell anemia and malaria.arrow_forward
- what fraction of the offspring of two parents with sickle trait would you expect to have sickle cell anemia? Explain how you arrived at this answer. Also include a punnet squarearrow_forwardDescribe the phenotype of individuals who inherit two copies of the HbS allele-Sickle Cell Disease. ( find a source to support the information)arrow_forwardSickle cell anemia is caused by an individual carrying two recessive copies of the hemoglobin gene (hemoglobin gene is labeled Hb, and the recessive version is Hbs). Thus, to have sickle cell anemia, a person must have the genotype HbSHbS. A person that is HbAHbA carries two copies of the normal hemoglobin gene and does not have sickle cell anemia. A person that is heterozygous (HbAHbS) produces enough normal hemoglobin to not have sickle cell anemia but is also resistant to malaria. People that are heterozygous are called “carriers” because they carry the recessive allele but do not express the recessive phenotype. a. A couple are both resistant to malaria but do not have sickle cell anemia. Draw a Punnett square to represent this cross. b. What is the probability that the couple has three children where one child does not have a recessive allele, one child is resistant to malaria and does not have sickle cell anemia, and one child has sickle cell anemia?arrow_forward
- The farmers in La Trinidad, Benguet have a remarkable ability to work in the cold without gloves and not suffer decreased skin blood flow. Does this prove that there is a genetic difference between the farmers in La Trinidad and the other people with regard to this characteristic?arrow_forwardExplain the differences between an individual homozygous for the sickle hemoglobin allele (HbS/HbS) and one who is heterozygous (HbA/HbS). Consider the hemoglobin molecule, cells, and disease.arrow_forwardThere is a benign congenital condition called Hereditary Persistence of Fetal Hemoglobin (HPFH) in which production of the fetal hemoglobin (HbF) is not switched off post-partum (after birth). It is due to a mutation in the β-globin gene cluster. People that are homozygotes for this mutation, meaning that the gene from both parents is mutated, continue to make almost exclusively HbF throughout their life rather than adult hemoglobin (HbA). HPFH homozygotes demonstrate a slight erythrocytosis, or an increase in the number or mass of their red blood cells, and consequently an increase in the concentration of HbF. Given only what you know about the oxygen saturation dynamics of HbF versus HbA, can you explain why there might be the slight erythrocytosis in HPFH homozygotes? It has been observed that the prevalence of HPFH is much higher in populations with certain hemoglobinopathic disorders such as sickle cell anemia, and is selected for in populations with a high prevalence of these…arrow_forward
- 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?arrow_forwardIn 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 generationarrow_forwardIn a hypothetical population, 16% have sickle-cell anemia. The population is in Hardy-Weinberg equilibrium. ( sickle-cell anemia is recessive) What is the frequency of the allele for sickle-cell anemia? What is the frequency of the allele for normal hemoglobin?arrow_forward
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