Reading Quiz Nov. 19 2012Chapter 15. 4—Linking genotypes and phenotypes : How beach mice go blond1. Thinking about the Central Dogma, how should we define the relationship between genotype and phenotype?a. Changes in the genotype can change the mRNA codons that are transcribed and the amino acids that are translated, leading to changes in the phenotype. 2. Functionally speaking, what is a mutation?a. Any permanent change in an organism’s DNA. 3. Why do mutations happen?a. Mutations can either cause disease or death or lead to increases in fitness, such as furnishing the heritable variation that makes evolution possible. 4. There are 4 classifications of mutations: describe the consequence of each one belowa. Silenti. Change in genotype but no change in phenotype. Usually neutral with respect tofitnessb. Missensei. Change in primary structure of protein may be beneficial, neutral, or deleteriousc. Nonsensei. Premature termination, polypeptide is truncated. Usually deleterious.d. Fameshifti. Reading frame is shifted, massive missense. Usually deleterious 5. Which class(s) of mutations are most likely to increase fitness?a. Missense Mutations 6. Which class(s) of mutation are most likely to decrease fitness?a. Nonsense and frameshift mutationsPlease read the paper posted on Courseweb: A single amino acid mutation contributes to Adaptive Beach Mouse Color pattern Hoekstra et al Science 2006 313:101 to answer the remaining questions7. Two populations of mice inhabit different environments along the Gulf coast, one group of mice have dark fur pigmentation whereas the other mice are light colored. The dark mice tend to live in the surrounding woodlands whereas the light colored mice occupy the dunes on the beach. These mice belong to the same family yet have different phenotypes—Why?a. Natural Selection for crypsis. 8. What environmental factor has determined the niche occupied by each variant mouse?a. The light colored mice adapt by natural selection for camouflage from predators, while the dark colored mice are more favorable for the darker mainland. 9. What explains the differences in the phenotypes of these mice?a. The dominant and recessive alleles account for the light color in the beach mice. 10. Do the respective phenotypes increase or decrease the fitness of the mice (where fitnessis defined as success in passing along one’s genes to one’ offspring)1Reading Quiz Nov. 19 2012a. Both phenotypes increase the fitness of the respective mice. 11. What is the function of the Mc1r gene?a. Mc1r plays a key role in melano- genesis by switching between the production ofdark eumelanin and light pheomelanin12. What type of protein does it specify?a. G protein13. How doesMc1r specify the phenotypes of these mice?a. By switching between the production of dark eumelanin and light pheomelanin14. What is a nucleotide polymorphism?a. A single, fixed nucleotide polymorphism (SNP) occurs between the two subspecies, resulting in a charge-changing amino acid variant in the first intracellular loop of MC1R 15. How is the dark allele related to the light allele of Mc1r?a. They are both created by the Mc1r gene through the production of dark eumelanin and light pheomelanin 16. What is the inheritance pattern of the light and dark alleles of Mc1r—which is dominant and which is recessive?a. The light allele is dominant while the dark allele is
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