Change Over Time First Name Last Name State Standard: H.2L.4 and H. 2 L.5 -- Explain how biological evolution is the consequence of the interactions of genetic variation, reproduction and inheritance, natural selection, and time, using multiple lines of scientific evidence. Response Scoring Rubric 10 Exceeds Evaluate the impact of the interactions of genetic variation, reproduction and inheritance, natural (excellent) selection and time on biological evolution (change) 8 Meets Explain how biological evolution is the consequence of the interactions of genetic variation, (proficient) reproduction and inheritance, natural selection, and time, using multiple lines of scientific evidence. 6 Nearly Meets Describe the process of biological evolution through natural selection Does Not Meet 4 Recognize that species have changed over time 1 Incomplete Did not participate Score Allelic Frequencies and Sickle- Cell Anemia ickle-cell anemia, a potentially fatal disease, results from a mutant allele for hemoglobin, the oxygencarrying protein on red blood cells. There are two alleles for the production of hemoglobin. Individuals with two Hemoglobin A alleles (AA) have normal red blood cells. Those with two mutant Hemoglobin S alleles (SS) have abnormal sickle- shaped red blood cells and suffer from sickle-cell anemia. Heterozygous (AS) individuals carry the mutant allele but do not suffer from its debilitating effects. They have both normal and sickle-shaped red blood cells. In the United Sates, about 1 in 500 African- Americans develops sickle-cell anemia. But in Africa, about 1 in 100 individuals develops the disease. Why is the frequency of a potentially fatal disease so much higher in Africa? The answer is related to another potential fatal disease, malaria. Individuals with an AA hemoglobin genotype have a significant greater risk of contracting malaria and may die from the disease. This results in the removal of Hemoglobin A alleles from the gene pool. The SS genotype, which results in sickle-cell anemia, is usually fatal before the age of twenty. This results in the removal of Hemoglobin s alleles from the population. A person with an AS genotype does not develop sickle-cell anemia and has less chance of contracting malaria. Such a person is better able to survive and reproduce in a malaria-infected region. Therefore, both the individual’s A allele and S allele remain in the population. The frequency of the Hemoglobin s allele in malaria-infected regions of Africa is 16%. But in the United States, where malaria has been eradicated, the allelic frequency is 4%. Simulate You will now simulate the fusion of gametes and record the resulting genotypes of each offspring, using all of the beans in the unlabeled container. You will also simulate the effect of being homozygous or heterozygous for the hemoglobin gene in a malaria-infected region. One team member will select two beans from the unlabeled container 50 times. After each selection, a second team member will indentify and record the genotype of the “offspring” in Table 1 by making a slash under the appropriate column head. The same team member then places each pair of beans in container AA, AS, or SS, depending on the genotype. During the periods when the blindfold team member is making a selection, the recorder will randomly call out the word “malaria” a total of 25 times. (This represents a 50% malaria infection rate.) if the genotype of the selected pair of gametes is AA, that offspring will contact malaria and die. Therefore, place that pair of alleles in the container labeled “Non-Surviving Alleles” and put a circle around the slash (that is, the recorded genotype) in table 1. If the genotype is AS, the individual will survive. Put a circle around the slash in Table 1, and place the pair of beans in the container labeled AS. If the genotype is SS, the individual will die. As with the individual homozygous for the normal Hemoglobin gene, place the beans in the container labeled “Non-Surviving Alleles” and draw a circle around the recorded genotype. S Procedure 1. Place 75 red beans in the unlabeled container (this is the 1st generation gene pool). These beans represent gametes carrying the Hemoglobin A allele. 2. Add 25 white beans to the unlabeled container (this is the 1st generation gene pool). These beans represent gametes carrying the Hemoglobin S allele. 3. Without looking, one partner should draw two beans out of the “gene pool”. The other partner records in Table 1. REMEMBER: 1 TICK MARK = 2 BEANS !!!!!!!!!!!!! 4. If two reds are selected (AA), place them in the AA container 5. If one red and one white are selected (AS), place them in the AS container. 6. If two whites are selected (SS), place them in the SS container. 7. Randomly (every other time) the recorder should call “malaria” to simulate the malaria infection rate of 50%. Circle the tick mark in Table 1 showing a “bite”. 8. Count the number of red beans and white beans in the unlabeled container and record the individual and combined totals in the appropriate spaces under Table 1. The combined total represents the total number of alleles for hemoglobin in the population. Calculate the allelic frequencies as shown and record your results. AA genotype Table 1 “Second Generation AS genotype SS genotype a. How many Red beans are remaining in the population? (remember: 1 tick = 2 beans) ____________A alleles b. How many White beans are remaining in the population? (remember: 1 tick = 2 beans) ____________S alleles c. What is the total number of alleles in the population? A+S= _________________ d. What is the frequency (percent) of the A allele? _________________ _ A__ x 100 = A+S e. What is the frequency (percent) of the S allele? _ S__ x 100 = _________________ A+S 9. After you have completed the cycle for one generation, you are ready to begin the next. All of the beans in the containers labeled AA and AS should be emptied into the unlabeled container. However, place all the beans from the container labeled SS into the container for “Non-Surviving Alleles” (Since individuals who are homozygous SS will not usually live long enough to have children, you will not use the SS gametes for tallying the next generation.) 10. To determine the 50% malaria infection rate for the generation of the population, take the total number of A and S remaining in the population and divide it by 4. This is the number of times you will randomly call out “malaria” in the next round of fusion of gametes. (For example, if you had 47 A and 17 S alleles in part “c” above, you would have a total of 64 alleles in the population. Divide this by 4 and you would get the number 16. This would be 50% of the next generation of people produced by the gamete fusions.) 11. Repeat the procedures you followed in step 5 and the step 6. Use Table 2 to record your data. 12. Repeat the procedures you followed in step 7. Record your data and calculation in the spaces provided under Table 2. AA genotype Table 2 Third Generation AS genotype SS genotype f. How many Red beans are remaining in the population? (remember: 1 tick = 2 beans) ____________A alleles g. How many White beans are remaining in the population? (remember: 1 tick = 2 beans) ____________S alleles h. What is the total number of alleles in the population? A+S= _________________ i. What is the frequency (percent) of the A allele? _ A__ x 100 = A+S _________________ j. What is the frequency (percent) of the S allele? _ S__ x 100 = A+S _________________ Analysis 1. a. What was the frequency of the A allele in the original population? ___75 %_______ b. What was the frequency of the S allele in the original population? _________________ c. What was the frequency of the A allele in the second population? _________________ d. What was the frequency of the S allele in the second population? _________________ e. What was the frequency of the A allele in the third population? _________________ f. What was the frequency of the S allele in the third population? _________________ g. Explain your findings. 2. Since few people with sickle-cell anemia are likely to survive to have children on their own, why hasn’t the Hemoglobin S allele been eliminated by natural selection? 3. Why is the frequency of the Hemoglobin S allele so much lower in the United States than in Africa? 4. Scientists are working on a vaccine against malaria. What impact would the vaccine have on the frequency of the Hemoglobin S allele in Africa? 5. Using your chapter 15 notes, which one of the 3 types of natural selection pressures are demonstrated in the lab? Circle one: Stabilizing Directional Disruptive Only answer the following if you’re going for a 10 6. Gradualism is the idea that species originate through a gradual change of adaptations over time. For this to work, some mutations must be favorable. What does “natural selection” say about favorable traits? 7. Adaptive radiation is the idea that an ancestral species can evolve into an array of species to fit a number of diverse habitats. Using the example of a donkey and a horse, why is the mule NOT a new species?