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Name ________________________________ Class _______ Date _________________ Sickle Cell Inheritance Use the virtual Genetics lab room to determine the pattern of inheritance of sickle cell disease. Lab Bench Used Sickle cell disease, also called sickle cell anemia, is a common genetic disorder. About 1 in 12 Americans of African heritage carry the allele for sickle cell. This allele is expressed in hemoglobin, the molecule that carries oxygen in red blood cells. In people with the disease, hemoglobin molecules clump together in long fibers, forcing the red blood cells, which are normally round, into long shapes that look like sickles. These sickle-shaped cells tend to get stuck in capillaries, slowing the distribution of oxygen to tissues and organs. Pain and fatigue are common symptoms, and organ failure can occur as well. A related condition called sickle cell trait has few if any harmful symptoms. People who have this trait actually have a heightened resistance to malaria, an infectious disease that has killed millions of humans, particularly in tropical areas where mosquitoes, which carry the disease, are abundant. In this lab activity, you will act as a genetics counselor. Using the virtual Genetics lab, you will determine how likely different sets of parents are to have children who will suffer from sickle cell disease. Enter the Virtual Bio Lab and select the title of this lab activity from the “Heredity” menu on the whiteboard. You will be taken to the virtual Genetics lab room. Part A: Finding the Pattern of Inheritance In the virtual Genetics lab, choose “Human” from the Species Selector and “SickleCell Anemia” from the menu of traits. Suppose a husband and wife come into your office. The husband is homozygous for the sickle cell allele, which means he suffers from sickle cell disease. The wife is homozygous for the normal allele. They wish to have children but are concerned about passing on sickle cell anemia. Set the parents’ alleles accordingly and set the number of offspring to the maximum of 6. Click the “Cross” button repeatedly until you can see the results for 100 offspring—a large enough sample size to determine the pattern of inheritance of the trait. Make sure the “Include Male/Female” box in the lower left corner of the results box isn’t checked. 1. What percentage of the F1 offspring has sickle cell trait, sickle cell anemia, and normal blood? ______________________________________________________________________ ______________________________________________________________________ Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Virtual Bio Lab 1 Heredity: Sickle Cell Inheritance Name ________________________________ Class _______ Date _________________ 2. What does this result suggest about the pattern of inheritance of sickle cell disease? ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ _____________________________________________________________________________ 3. How would you counsel this particular couple about their would-be offspring? What about their offspring’s offspring? ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ _____________________________________________________________________________ 4. Complete the three Punnett squares below to illustrate how likely this couple’s children are to produce offspring with sickle cell trait or disease. (A represents the normal allele; S represents the sickle cell allele.) Use the virtual Genetics lab to run these crosses and confirm the accuracy of your Punnett squares. To the right of each square, give the percentages of offspring that will be normal, carriers (sickle cell trait), and sufferers of sickle cell disease. Homozygous normal Scenario 1 A Heterozygous (carrier) A Percentage normal offspring: Percentage with sickle cell trait (carriers): A Percentage with sickle cell disease: S Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Virtual Bio Lab 2 Heredity: Sickle Cell Inheritance Name ________________________________ Class _______ Date _________________ Heterozygous (carrier) Scenario 2 A Heterozygous (carrier) Percentage normal offspring: A Percentage with sickle cell trait (carriers): S Percentage with sickle cell disease: Homozygous for sickle cell allele Scenario 3 S Heterozygous (carrier) S S Percentage normal offspring: A Percentage with sickle cell trait (carriers): S Percentage with sickle cell disease: Part B: Evolution and the Sickle Cell 5. It’s harmful to have two sickle cell alleles, but in a region where malaria is prevalent, having one sickle cell allele can be beneficial. Look at the phenotype breakdown of the offspring in each of the three scenarios above. Which phenotype is most common overall? ______________________________________________________________________ ______________________________________________________________________ _____________________________________________________________________________ 6. Explain how a population in a region affected by malaria could derive more benefit than harm from the presence of the sickle cell allele. ______________________________________________________________________ ______________________________________________________________________ Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Virtual Bio Lab 3 Heredity: Sickle Cell Inheritance Name ________________________________ Class _______ Date _________________ _____________________________________________________________________________ Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Virtual Bio Lab 4 Heredity: Sickle Cell Inheritance