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Name: _______________________________________________________________ Class: ____________ Biology 9 - Genetics Case Study: Albinism in the Bowman Family Overview: The Bowman family makes an excellent case study for genetic inheritance for two reasons. First, they have a really big family. This allows us to see the effects of probability on each offspring more easily. Secondly, some members of the Bowman family have an interesting genetic trait – albinism. Albinism is a genetic condition characterized by a lack of pigment which results in extremely light skin, hair, and eyes. Your task in this case study is to analyze some information about the Bowman family in order to determine the genetic inheritance pattern of albinism. Is it dominant, recessive, or codominant? Or is it controlled by more than one genes (polygenic)? You are also responsible for determining the genotype of key members of the Bowman family, and then for doing some further genetic analysis of the traits that they show. This case study is structured like a formal lab report in that you will gather background information, make a hypothesis, work with data, do some analysis, and form some conclusions. However, you will not actually type up the lab report – all the work will be completed in this packet. Page | 1 Background Information – Notes: Take notes here based on Ms. Bowman’s presentation! Background Information - Paragraph: Use the space below to write a well-connected paragraph that explains important background information about albinism and/or the Bowman family. _____________________________________________________________________________________________ _____________________________________________________________________________________________ _____________________________________________________________________________________________ _____________________________________________________________________________________________ _____________________________________________________________________________________________ _____________________________________________________________________________________________ _____________________________________________________________________________________________ _____________________________________________________________________________________________ _____________________________________________________________________________________________ _____________________________________________________________________________________________ _____________________________________________________________________________________________ _____________________________________________________________________________________________ _____________________________________________________________________________________________ Page | 2 Purpose & Hypothesis: The purpose of this case study is to ____________________________________________________________________ _________________________________________________________________________________________________ Hypothesis: Do you predict that albinism is dominant, recessive, codominant, or polygenic? ___________________________ Why? ______________________________________________________________________________________ ___________________________________________________________________________________________ Procedure & Data 1. On the next page, draw a pedigree diagram representing the Bowman family. In a pedigree diagram: Circles represent females and Squares represent males Horizontal lines connecting two people mean that they had children together Vertical lines connect parents with their offspring Shaded shapes mean that the person has the trait you are studying An example pedigree diagram is on the board. o Use the table on page 5 to guide you – it has all the necessary information about the Bowman family that you’ll need to make your pedigree. o Your pedigree diagram should have a title and a key. o You may want to turn the paper sideways and draw your pedigree going across the long way on the page, so that you have enough room. Page | 3 2. Before moving on, get your pedigree approved by your instructor: ___________ Page | 4 Use the information in this table to make your pedigree: THE BOWMAN FAMILY – 3 Generations Name Parents Phenotype Mom light brown hair, green eyes Dad dark brown hair, blue eyes Possible genotype(s) for albinism Possible genotype(s) for hair and eye color Children (in order, eldest to youngest) Billy light brown hair, brown eyes Mike has albinism Betsy (Ms. Bowman) has albinism Meg light brown hair, hazel eyes Tricia has albinism JJ dark brown hair, blue eyes Chris dark brown hair, brown eyes Bobby dark brown hair, blue eyes Peter light brown hair, blue eyes Some of the spouses and grandchildren Tricia’s family: Brian (husband) dark brown hair, brown eyes Joseph (son) dark brown hair, brown eyes Lucy (daughter) dark brown hair, brown eyes Olivia (daughter) dark brown hair, brown eyes Chris’s family: Isabelle (wife) blond hair, blue eyes Jack (son) blond hair, blue eyes Leo (son) blond hair, blue eyes Page | 5 3. Now you need to study your pedigree and figure out the inheritance pattern of albinism. Is albinism a dominant trait? A recessive trait? Or is something different (such as codominance or polygenics) going on? You may want to get some scrap paper and try out different Punnett Squares until you find one that works. Basic Conclusions: What is the inheritance pattern of albinism – is it dominant, recessive, or something else? Explain in detail your reasoning for your answer. You may want to refer to a Punnett Square, which you will draw below. __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ What are the genotypes of… Dad Bowman __________ Mom Bowman __________ Use their genotypes to draw a Punnett Square showing the possible offspring that they could have: Now go back to the table on page 5. Fill in the possible genotypes for each member of the family. For some, you should be able to write one definite genotype. For others, you should write as many possibilities as it could be. Analysis 4. Compare your conclusion for the inheritance pattern of albinism with your hypothesis. Was your hypothesis correct? _______ If not, explain why it was wrong: Page | 6 5. What is the actual proportion (or percentage) of Bowman children (ignore the spouses and grandchildren for this question) who have albinism, out of all of Mr. and Mrs. Bowman’s kids? ______________________ What is the expected proportion (or percentage) of Mr. and Mrs. Bowman’s children that were likely to have albinism, based on your Punnett Square? ______________________ How closely do the actual numbers match your predictions? Is this expected or unexpected? Explain your answer. _______________________________________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________ 6. Compare two sets of Bowman grandchildren – Trisha’s kids and Chris’s kids. a. What are the chances that Trisha’s kids are carriers (this means they are heterozygous but don’t show the trait) for albinism? Explain your answer! b. What are the chances that Chris’s kids are carriers for albinism? (This one is a little trickier to figure out – explain either in words or some probability math) Page | 7 7. Michael (the 2nd Bowman child) is married to Alysia. Alysia is of Chinese descent, so she has black hair and dark brown eyes. They do not have any children yet. a. What is Alysia’s most likely genotype for albinism? ___________ b. Assuming that you are correct, draw a Punnett Square showing how the albinism allele will be passed down to Michael and Alysia’s future children: c. What is the probability that Michael and Alysia will have a child with albinism? _________ d. What is the probability that they will have a child who is a “carrier” (this means heterozygous) for albinism? _________ 8. Dark brown hair (D) is dominant over light brown hair (d). Blue eyes (e) are recessive, so anyone with another color has at least one dominant allele (E). a) In the table on page 5, fill in the final column of genotypes for hair color and eye color for all family members except those with albinism. (Hint: start with Peter! Then figure out the parents, and then fill in everyone else.) b) Make a Punnett square showing predicted ratios of genotypes and phenotypes for hair and eye color in the Bowman children, based on their parents’ genotypes. Make sure you write the predicted ratios for every combination of hair/eye colors after you draw your Punnett Square. c) How closely do the actual numbers of children match these predictions? Bonus: Read the article entitled “Albino Like Me,” which was published in the Boston Globe a couple of years ago. Then answer the questions at the end of the article. Page | 8