Concept explainers
Neanderthal Hair Color The MC1R gene regulates pigmentation in humans (Sections 14.1 and 15.1 revisited), so loss-of-function mutations in this gene affect hair and skin color. A person with two mutated alleles for this gene makes more of the reddish melanin than the brownish melanin, resulting in red hair and pale skin. DNA extracted from two Neanderthal fossils contains a mutated MC1R allele that has not yet been found in humans. To see how the Neanderthal mutation affects the function of the MC1R gene. Carles Lalueza-Fox and her team introduced the allele into cultured monkey cells (FIGURE 26.16).
FIGURE 26.16 MC1R activity in monkey cells transgenic for an unmutated MC1R gene, the Neanderthal MC1R allele, or the gene for green fluorescent protein (GFP). GFP is not related to MC1R.
1. How did MCR1 activity in monkey cells with the mutant allele differ from that in cells with the normal allele?
Want to see the full answer?
Check out a sample textbook solutionChapter 26 Solutions
Biology: The Unity and Diversity of Life (MindTap Course List)
- Neanderthal Hair Color The MCIR gene regulates pigmentation in humans (Sections 14.1 and 15.l revisited), .so loss-of-function mutations in this gene affect hair and .skin color. A person with two mutated alleles for this gene makes more of the reddish melanin than the brownish melanin, resulting in red hair and pa le skin. DNA extracted from two Neanderthal fossils contains a mutated MC1R allele that has not yet been found in humans, To see how the. Neanderthal mutation affects the function of the MC1R gene, Carles Lalueza-Fox and her team introduced the allele into cultured monkey cells (FIGURE 26.1 6). FIGURE 26.16 MC1R activity in monkey cells transgenic for an unmutated MClR gene, the Neanderthal MC1R allele or the gene for green fluorescent protein (GFP). GFP is- not related to MC1R. What purpose do the cells with the gene for green fluorescent protein serve in this experiment?arrow_forwardGene Interaction and Epistasis Hair color is due to the presence of melanin. There are two types of melanin produced by melanocytes. One is eumelanin, which is responsible for black (homozygous), brown (heterozygous), and blond (recessive) hair colors. The other is pheomelanin, which is responsible for red hair color. During melanin synthesis, MCR1gene converts pheomelanin to eumelanin. However, a variant of the MCR1 gene (MCR1variant), prevents this conversion. A cross between a blond-haired mother and a red-haired father produced 100% brown-haired children. When they came of age, one child married a double heterozygote, and both were blessed with 7 children; 2 with black hair, 2 with brown hair, 1 with blond hair, and 2 with red hair. Using the 7-step method, determine the genotypes of the P1, the F1, and the F2s. BOX your answers (if handwritten) or HIGHLIGHT your answers (if encoded). STEP 1: ________________________________________________________ STEP 2:…arrow_forwardWhat type of mutation is this? 1. Which type of mutation is responsible for new varia tions of a trait? Which type of mutation does not result in an abnormal amino acid sequece? Which type of mutation stops the translation of an mRNA molecule? 2. Sickle Cell Anemia Sickle cell anemia is the result of a type of mutation in the gene that codes for part of the hemoglobin molecule Hemoglobin carries oxygen in your red bloods cells. The mutation causes these red blood cells to become stife sickle-shaped when they release their oxygen. The sickled cells tend to get stuck in blood vessels, causing poin ond increased risk of stroke, blindness, damage to the heart & lungs, and other conditions. Analyze the DNA strands below to determine what amino acid is changed AND what type of mutation occurred Normal hemoglobin DNA A G TC Normal hemoglobin mRNA val• Hisolelo thr•proo Gll Normal hemoglobin AA sequence CA cGT AG A CTGAGG AC AC Sickle cell hemoglobin DNA Sickle cell hemoglobin mRNA Sickle cell…arrow_forward
- Comparisons between human and chimpanzee genomes indicate that a gene that may function as a wild-type or normal gene in one primate may function as a disease-causing gene in another [The Chimpanzee Sequencing and Analysis Consortium (2005). Nature 437:69–87]. For instance, the PPARG locus (regulator of adipocyte differentiation) is a wild-type allele in chimps but is clearly associated with Type 2 diabetes in humans. What factors might cause this apparent contradiction? Would you consider such apparent contradictions to be rare or common? What impact might such findings have on the use of comparative genomics to identify and design therapies for disease-causing genes in humans?arrow_forwardThe flower color of genetically identical hemp plants (clones) is purple when the flowers develop under cold environment (30 °C). Describe in detail a molecular mechanism that could explain how these two groups of genetically identical plants differ in their gene expressions to produce different flower colors?arrow_forwardOriginal DNA Sequence: TACAC CTTGG CGACGACT... MRNA Sequence: Amino Acid Sequence: Mutated DNA Sequence #5 TACACCTT G G GACGACT... (Highlight the change) What's the mRNA sequence? What will be the amino acid sequence? Will there likely be effects? What type of mutation is this? 1. Which type of mutation is responsible for new variations of a trait? 2. Which type of mutation does not result in an abnormal amino acid sequence? 3. Which type of mutation stops the translation of an mRNA molecule? NOarrow_forward
- . The physicist Stephen Hawking, famous for his theories about black holes, has lived past the age of 70 withamyotrophic lateral sclerosis (ALS), a paralyzing neurodegenerative disease that is usually fatal at a muchyounger age. Recently, geneticists discovered that amajor cause of ALS is the unusual expansion of ahexanucleotide repeat (5′-GGGGCC-3′) that lieswithin a gene called C9ORF72, at a location outside ofthe gene’s open reading frame (ORF). A single expanded allele is sufficient to cause ALS, but the reasonthe disease allele is dominant remains unclear. Someexperimental results support the theory that the allelemakes a toxic RNA containing the expanded repeat. Ifthis theory is correct, in what ways is the mutant ALScausing allele similar to the mutant allele that causesHuntington disease? In what ways is it similar to themutant allele that causes fragile X syndrome?arrow_forwardSynpolydactyly is an abnormality characterized by webbing between partially or completely duplicated fingers or toes (Figure 18.15). The same mutations that cause the human phenotype give rise to a similar phenotype in mice. In what family of genes do you think these mutations occur?arrow_forwardThe disease called phenylketonuria (PKU) is a recessive disorder in humans that is due to a loss-of-function mutation involving the gene that encodesphenylalanine hydroxylase. Some people with the disorder carrya point mutation that causes the loss of function, whereas otherindividuals have been shown to have a deletion of the entire gene. Explainhow you could use fluorescence in situ hybridization to distinguish apoint mutation from a deletion. Describe your expected results.arrow_forward
- When the human genome sequence was finally completed, scientists were surprised to discover that the genome contains far fewer genes than expected. How many genes are present in the human genome? Scientists have also found that there are many more different kinds of proteins in human cells than there are different genes in the genome. How can this be explained?arrow_forwardVariations in Phenotype Expression A genetic disorder characterized by falling asleep in genetics lectures is known to be 20% penetrant. All 90 students in a genetics class are homozygous for this gene. Theoretically, how many of the 90 students will fall asleep during the next lecture?arrow_forwardGenetically Modified Foods The creation of transgenic crop plants using recombinant DNA methods involves the transfer of just one gene or a small number of genes to the plants, in contrast to classical breeding methods in which hundreds or even thousands of genes are transferred at once. Explain why this is true. If fewer genes are transferred during the creation of transgenic crops, why are some people afraid that they are dangerous?arrow_forward
- Biology: The Unity and Diversity of Life (MindTap...BiologyISBN:9781305073951Author:Cecie Starr, Ralph Taggart, Christine Evers, Lisa StarrPublisher:Cengage LearningBiology Today and Tomorrow without Physiology (Mi...BiologyISBN:9781305117396Author:Cecie Starr, Christine Evers, Lisa StarrPublisher:Cengage LearningHuman Heredity: Principles and Issues (MindTap Co...BiologyISBN:9781305251052Author:Michael CummingsPublisher:Cengage Learning