Question 1.4.3 Hembwork Rhiwered How did the frequencies of the lactase persistence and sickle cell phenotypes change as a result of genetic drift? Was this change the result of some individuals being better able to survive than others? Is it possible that genetic drift can cause the same change in the poputation as naturat setection? Why? Why not?
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4.3 Homework Answered How did the frequencies of the lactase persistence and sickle cell phenotypes change as a result of genetic drift? Was this change the result of some individuals being better able to survive than others? Is it possible that genetic drift can Show more…
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Part IV - Tracing the Origin of the Lactase Persistence Trait Sanjeet: I wonder what caused the evolution of something like lactase persistence in humans? Xiao-Ma: Well, I think that's pretty obvious, right? Chris: Really? It's not to me. You have to explain that to me. Xiao-Ma: Well, in my biology class, we learned that after a new trait arises from a genetic mutation, it may become prevalent in a population if it is advantageous for individuals to have it. Chris: That's still over my head. Xiao-Ma: Well, if it's better for the survival of the individual and the species, then whatever trait gave them the advantage will become more prevalent in the population because those individuals reproduce more successfully. Sanjeet: Wait a minute, are you saying I won't reproduce successfully because I'm lactose intolerant? Xiao-Ma: Now you're being silly. Let's think about this from more of an evolutionary and historical standpoint. Questions: 1. What role do mutations play in the evolution of new traits such as lactase persistence? 2. What role does the environment play in the evolution of new traits such as lactase persistence? 3. How can a mutation become more prevalent in certain populations if it's better for the survival of the population? 4. If mutations are random and equally likely in each of these populations, why are there no known mutations in the lactase gene itself in lactose intolerant populations? 5. Why do you think that some populations developed lactase persistence? Using these terms, draw a map of how they might connect to each other. Terms: environmental factors, diet, dairy farming, changes in DNA, phenotype, genotype, traits, mutation. 6. Optional: How would you calculate the percentage of individuals with a particular trait in a population knowing certain parameters?
Josee P.
radioisotope to decay, +Estimate the age by measuring content. Fossils contain Carbon can be easily dated with how much radiocarbon is in that fossil Chap. 17 10. Explain how malaria and sickle-cell anemia is part of an example of balanced polymorphism. What are the selective pressures acting on the different alleles? maintenance of 2 or more alleles for a trait at high frequency in a population against homozygotes HbA/HbS heterozygets individuals are more likely to survive than HbA/HbA homozygotes. 11. Genetic drift is a change in allele frequencies due to chance alone. Genetic drift can be much more pronounced in small populations. Genetic drift can result from a bottleneck, the founder effect or inbreeding. Ex. Although there are as many starlings in North America as there are in Europe, genetic variability in the North American population is reduced relative to that in Europe because only a few starlings made it to North America from the parent population in Europe. This is an example of the founder effect
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1. How does genetic drift change with population size? 2. How does the strength of selection affect the probability that an allele will disappear when the allele starts at a low frequency? 3. How does selection for heterozygotes affect the chance of an allele disappearing in a small population? 4. Human mutation rates are generally around 0.000001 at a particular locus. Will mutation at that rate affect whether a population is in Hardy-Weinberg equilibrium?
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