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
Campbell Biology (11th Edition)
Additional Science Textbook Solutions
Concepts of Genetics (12th Edition)
Microbiology with Diseases by Taxonomy (5th Edition)
Biology: Life on Earth
Biology: Life on Earth with Physiology (11th Edition)
Human Biology: Concepts and Current Issues (8th Edition)
Campbell Biology: Concepts & Connections (9th Edition)
- Recall from our classes on molecular evolution that some proteins evolve more rapidly than others. For example, the oxygen-carrying protein myoglobin evolves more quickly than the D1 protein of photosystem II. What explains this difference in the rate of protein evolution? A. Proteins like myoglobin have evolved more recently than proteins like D1 and thus have been forced to evolve more quickly. B. Changes to the sequence of some proteins can be tolerated as they don’t alter fitness; for other proteins, sequence changes are usually harmful. C. In constrained proteins like D1, evolution results primarily from nucleotide changes that alter the amino acid sequence of the protein. D. Protein evolution is dependent upon the rate of gene mutation and some genes have a higher rate of mutation than others.arrow_forwardBackground: In class we did a project about m and m’s and there ability to evolve and natural selection. (Yes I know they can’t actually evolve it was just used as a example in class) however I can’t figure out this question. Occasionally a mutant may occur and produce a candy that is misshapen or Pointier or flatter than the rest. Often this proves to be a weakness, but a rare mutation may confer extra M&M durability. Other mutations in M&Ms could occur ( like ones that result in a new color). A mutant un you population represents a new _________. What goes in the blankarrow_forwardQ5.1. 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_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_forwardFollowing a gene duplication, two genes will accumulate different mutations, causing them to have slightly different sequences. In Figure 8.7, which pair of genes would you expect to have more similar sequences: α1 and α2 or ψα1 and α2? Explain your answer.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_forward
- Just as anatomical homology can lead to vestigial structuressuch as human wisdom teeth and the wings of flightlessbirds, genetic homology can lead to vestigial DNA sequences.For example, most mammal species produce an enzyme,L-gulonolactone oxidase, that catalyzes the last step in the productionof vitamin C. The species that produce the enzyme areable to do so because they all inherited the gene that encodesit from a common ancestor. Humans, however, do not produceL-gulonolactone oxidase, so we can’t produce vitamin C ourselvesand must consume it in our diets. But even though wedon’t produce the enzyme, our cells do contain a stretch of DNAwith a sequence very similar to that of the enzyme-producinggene present in rats and most other mammals. The human version,though, does not encode the enzyme (or any protein). Weinherited this stretch of DNA from an ancestor that we share withother mammal species, but in us, the sequence has undergonea change that rendered it nonfunctional. (The…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_forwardA 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_forward
- Which 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_forward2b)An ancient gene underwent duplication during the course of evolution to yield two chain genes designated as δ and ε genes. Jessica’s final year project deals with the metagenomic studies of anfH homologous genes from freshwater lake samples in Kampar Eastlake. She successfully cloned and sequenced two partial anfH homologous gene sequences.BlastX analyses revealed that one of the DNA sequences showed highestsimilarity to AnfH protein from a Brazilian soil bacteria isolate while the second sequence showed highest identity to the AnfH protein sequence of a bacterium that was isolated from Tonle Sap, a freshwater lake in Cambodia. To determine their evolutionary relationship, she subsequently constructed a phylogenetic tree using the corresponding protein sequences. Describe the steps that are required toperform the analysis.arrow_forwardEvolution in Humans 1) explain what evolutionary mechanisms are involved in creating variation in populations 2) define homology and analogy and discuss examples of eacharrow_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