Concept explainers
MAKE CONNECTIONS Ø The gene that causes sickle-cell disease is present in a higher percentage of residents of sub-Saharan Africa than among those of African descent living in the United States. Even though this gene causes sickle-cell disease, it also provides some protection from malaria, a serious disease that is widespread in sub-Saharan Africa but absent in the United States. Discuss an evolutionary process that could account for the different percentages of the sickle-cell gene among residents of the two regions. (See Concept 1.2.)
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Chapter 1 Solutions
EBK CAMPBELL BIOLOGY
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Biology: Life on Earth (11th Edition)
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Human Biology: Concepts and Current Issues (8th Edition)
- Q5.1. Which of the following is FALSE? O If a genetic disease reduces fertility and the allele that causes the disease offers no other advantage, the allele will likely eventually disappear, due to natural selection. Natural selection does not favor individuals who are homozygous for the sickle-cell allele, because these individuals typically die before they are old enough to reproduce. Individuals who are heterozygous HbAlHbS are protected from malaria, and this is why sickle-cell disease persists in wetter, mosquito-prone regions in Africa. O In regions where malaria does not occur, individuals who are heterozygous HbAIHbS have a fitness advantage over those who are homozygous for the normal hemoglobin allele (HbA).arrow_forwardIf myoglobin is found in all chordates, urochordates, and cephalochordates, b-globin is found in all vertebrates, a-globin in all ostracoderm descendants, z-globin in all gnathostomes, e-globin in all viviparous mammals, and g-globin in all placental mammals, then the most ancient of these genes: must be epsilon-globin (e-globin), found only in descendants of the ancestral marsupials must be myoglobin, found only in descendants of the chordates, urochordates, and cephalochordates must be gamma-globin (g-globin), found only in descendants of the ancestral placentals must be zeta-globin (z-globin), found only in descendants of the ancestral gnathostome fishes must be beta-globin (b-globin), found only in descendants of the ancestral vertebratesarrow_forwardSickle Cell Anemia: An Application of Hardy-Weinberg and Chi-square analysis Scenario 1: In nature, not all genotypes have the same rate of survival; that is, the environment might favor some genotypes while selecting against others. This is the essence of natural selection. An example is sickle-cell anemia, a disease caused by a single gene mutation. Individuals who are homozygous recessive (a/a) for the sickle cell allele often do not survive to reach reproductive maturity. Your question for this analysis is "Does evolution cause a significant decrease in the frequency of sickle cell disease?" 1. What is the null hypothesis? 2. Assume there is a population of 1,000 people. According to the null hypothesis, what is the expected # of people with and without sickle cell disease in the population? 3. Using your answer from #2 above, calculate the expected proportion of individuals with the homozygous recessive (aa), heterozygous (2pq), and homozygous dominant (AA) genotypes. with sicklearrow_forward
- Why do scientists believe that the sickle-cell trait has not evolved out of the human population yet considering how deadly it is to be homozygous for the sickle cell gene?arrow_forwardIf 9% of an African population is born with a severe form of sickle-cell anemia (ss), what percentage of the population will be more resistant to malaria because they are heterozygous (Ss) for the sickle-cell gene? Assume Hardy-Weinberg conditions. Submit your answer as it is. a) homozygous recessive individuals (q²) b) the recessive allele (q) c) the dominant allele (p) d) homozygous dominant individuals (p²) e) heterozygous individuals (2pq)arrow_forward2a)An ancient gene underwent duplication during the course of evolution to yield two chain genes designated as δ and ε genes. What is the name of A,B,C and the contrast between B and C.arrow_forward
- A form of dwarfism known as Ellis–van Creveld syndrome was first discovered in the late 1930s, when Richard Ellis and Simon van Creveld shared a train compartment on the way to a pediatrics meeting. In the course of conversation, they discovered that they each had a patient with this syndrome. They published a description of the syndrome in 1940. Affected individuals have a short-limbed form of dwarfism and often have defects of the lips and teeth, and polydactyly (extra fingers). The largest pedigree for the condition was reported in an Old Order Amish population in eastern Pennsylvania by Victor McKusick and his colleagues (1964). In that community, about 5 per 1000 births are affected, and in the population of 8000, the observed frequency is 2 per 1000. All affected individuals have unaffected parents, and all affected cases can trace their ancestry to Samuel King and his wife, who arrived in the area in 1774. It is known that neither King nor his wife was affected with the…arrow_forwardWhich of the following proteins is thought to have been the first to evolve from an ancestral gene duplication of the most ancient O2 transporting protein in vertebrate hemoglobin (found today in all vertebrates except the agnathan fishes)? A. gamma-globin (-globin) B. epsilon-globin (-globin) C. alpha-globin (-globin) D. delta-globin (-globin) E. zeta-globin (-globin)arrow_forwardPLEASE ANSWER THE QUESTION AND EXPLAIN SUCCINTLY IN 2 SENTENCESarrow_forward
- MAKE CONNECTIONS In a region free of malaria, would individuals who areheterozygous for the sickle-cell allele be selected for or selected against? Explain.arrow_forwardOnce nuclear DNA sequencing became fast and able to handle sequencing ancient DNA, living humans were found to have some Neanderthal genes. Is this finding clear evidence that some early modern humans did indeed hybridize with Neanderthals? Why?arrow_forwardWhat is the answer to this problem? I said the answer was "Homo sapiens populations interbred with the Denisovans before leaving Africa." and this was marked wrong.arrow_forward
- Biology: The Dynamic Science (MindTap Course List)BiologyISBN:9781305389892Author:Peter J. Russell, Paul E. Hertz, Beverly McMillanPublisher:Cengage LearningBiology (MindTap Course List)BiologyISBN:9781337392938Author:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. BergPublisher:Cengage Learning