Pedigree Studies. Opening Activity: Latin Root Word: Review of Old Information: Guinea pigs can have curly or straight hair, where the curly gene is

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1 Section: 3.7 Opening Activity: Latin Root Word: Name: Review of Old Information: Guinea pigs can have curly or straight hair, where the curly gene is recessive. Guinea pigs can also have a condition called bowlegged, where their legs curve noticeably outward. Bowleggedness is a dominant lethal allele if an individual inherits two copies of it (BB). Show the cross between a curly haired, bowlegged guinea pig and a heterozygous straight haired pig that is also bowlegged. How many of their offspring would you expect to be normal with curly hair? Pedigree Studies Background Information: Pedigrees are not reserved for show dogs and race horses. All living things, including humans, have pedigrees. A pedigree is a diagram that shows the occurrence and appearance, or phenotype of a particular genetic trait from one generation to the next in a family. Genotypes for individuals in a pedigree usually can be determined with an understanding of inheritance and probability. In this investigation you will: Pedigree Notes Pedigree = a. learn the meaning of all the symbols and lines that are used in a pedigree b. determine expected genotypes for all individuals shown in a pedigree.

2 are identified by Roman numerals An affected mother and an unaffected father have 3 children. The mother has a autosomal recessive disorder. One of the children marries a carrier. What is the probability that their child will be affected? (draw the pedigree in you notes) Autosomal Recessive Trait is in pedigree Trait often generations (hidden in carriers) Trait affects males and females (so not sex linked)

3 Autosomal Dominant Trait is in the pedigree Trait is found in generation Affected individuals transmit the trait to ~ of their children (regardless of sex) No Carriers What is the inheritance pattern of the following pedigree? Use your notes and the Background Information above to answer the following questions: 1. What can usually be determined when using a pedigree? 2. In a pedigree chart, what do the following represent: Roman numerals Numbers Squares Circles Horizontal lines Vertical lines

4 Procedure: For all the pedigrees in this worksheet, the trait being shown is earlobe shape. Geneticists recognize two general earlobe shapes; free lobes and attached lobes (see Figure 1 below). The gene responsible for free earlobes (E) is dominant over the gene for attached earlobes (e). Reading a Pedigree: Figure 2 Use Figure 2 to answer the following questions: 1. What is the sex of the oldest child? 2. What is the sex of the youngest child? Use Figure 3 (the same family as in Figure 2, but at a later time) to answer the following questions: Figure 3 3. Which person is the son-in-law (Name him by generation # and person #)? 4. To whom is he married (Name her by generation # and person #)? 5. What sex is their child? Determining Genotypes from a Pedigree: To predict the genotypes for each person on a pedigree showing inheritance of a RECESSIVE TRAIT, there are two rules you must follow:

5 Rule 1: Assign two recessive genes to any person on a pedigree whose symbol is shaded. (These persons show the recessive trait being studied). Two small letters (in this case ee) are written below that person s symbol. Rule 2: Assign one dominant gene to any person on a pedigree whose symbol is unshaded. (These persons show the dominant trait being studied). A capital letter (in this case E_) is written below that person s symbol. Use these rules to predict the genotypes for the individuals in Figure 4 below. Figure 4 6. What is the genotype of I-1? 7. What is the genotype of II-3? 8. What is the genotype of II-4? 9. Could child II-3 or II-4 be EE yes/no? To predict the genotype for person II-1, a different method must be used. 10. Can an EE person married to an ee person (II-2), have children with free lobes (EE or Ee) yes/no? Do the Punnett square to prove your answer. 11. Can an Ee person married to an ee person (II-2), have children with free lobes (EE or Ee) yes/no? Do the Punnett square to prove your answer.

6 In this case, the genotype for person II-2 would be ee. At some time in the future, you might be able to predict the father s genotype. For example, if they have some children with attached earlobes (ee), then he must be Ee. Examine this pedigree: 12. Which Punnett Square, A, B, or C, would best fit this family circle one? E e E e E E E EE Ee E EE Ee E EE E EE Ee e Ee ee E E EE EE EE A B C 13. Explain your choice. 14. Examine the pedigree below predict the genotypes for each person. Write the letters on the lines provided remember the 2 rules! Answer the following questions about the pedigree in Question #4. a. How many generations are shown? b. How many persons have free earlobes just write a number? c. How many persons have attached earlobes just write a number? d. Identify by generation and person number, those people with attached earlobes.

7 1. Below is a pedigree for an inherited autosomal recessive lung disease. Provide the genotypes of each of the individuals marked with lower case letters. 2. Below is a pedigree for an inherited autosomal dominant brain disease. Provide the genotypes of each of the individuals marked with lower case letters.

8 3. Below is a pedigree for an inherited autosomal recessive heart disease. What is the probability that their child F would have the inherited heart disease?