Name _ Exercise 6: Pedigree Analysis [Adapted from TIBBETTS, MICHAEL F Program, Bard College, 1994.] Pedigree analysis with PTC paper Biology INTRODUCTION Mendel's methodical crosses were made possible by the ease with which parental types can be controlled in peas However, humans not lend themselves to the types of procedures that peas Even without considering the impossibility of controlled mating, the generation time is so long that directed studies would not be feasible We must, therefore, employ special methods in the analysis of human inheritance patterns The analysis of the pedigree, a symbolic representation of a family history, is a classic method of genetic analysis in humans Using carefully constructed pedigrees, we can determine whether a given allele is behaving as a dominant or a recessive trait and whether the gene is sex-linked In some special cases we can also determine if it is linked (not assorting independently) to some other gene The pedigree consists of a set of symbols that convey information about the incidence of a trait in successive generations Figure summarizes the symbols that are most commonly seen in a pedigree Monday, February 02, 2009 Page 45 6:40:06 PM BIO 114: BIOLOGY OF NONINFECTIOUS DISEASE — LABORATORY MANUAL EXERCISE 6: PEDIGREE ANALYSIS Figure Key to symbols commonly seen in pedigrees PROCEDURE, PART I: There are four hypothetical pedigrees printed on the next two pages Identify the type of inheritance pattern observed in each (dominant vs recessive; sex linked vs autosomal) At least one pedigree has no clear Mendelian pattern, and this should be noted, too Label individuals in each pedigree with their apparent genotype (AA = homozygous dominant, Aa = heterozygous, aa = homozygous recessive) There are some individuals in each that you cannot be certain of In those cases give the potential genotypes This portion of the laboratory can be handed in today for five points Monday, February 02, 2009 Page 46 6:40:06 PM BIO 114: BIOLOGY OF NONINFECTIOUS DISEASE — LABORATORY MANUAL EXERCISE 6: PEDIGREE ANALYSIS PEDIGREE NO 1: Is there a clear pattern of inheritance? If so, is the trait dominant or recessive? Is it sex-linked? PEDIGREE NO 2: Is there a clear pattern of inheritance? If so, is the trait dominant or recessive? Is it sex-linked? Monday, February 02, 2009 Page 47 6:40:06 PM BIO 114: BIOLOGY OF NONINFECTIOUS DISEASE — LABORATORY MANUAL EXERCISE 6: PEDIGREE ANALYSIS PEDIGREE NO 3: Is there a clear pattern of inheritance? If so, is the trait dominant or recessive? Is it sex-linked? PEDIGREE NO 4: Is there a clear pattern of inheritance? If so, is the trait dominant or recessive? Is it sex-linked? Monday, February 02, 2009 Page 48 6:40:06 PM Name _ PROCEDURE, PART II: The second part of the lab is to create a pedigree for your family If nothing else this exercise will give an idea of the challenge researchers who need to make pedigrees face Phenylthiocarbamide (PTC) is a chemical that has a bitter taste to some people and no taste at all to others.1 You will be supplied with both PTC impregnated paper strips (A) and control (non-PTC impregnated) paper strips (B) Test as many family members as you can with each sheet Try to get siblings, parents, maternal and paternal grandparents, and maternal and paternal aunts, uncles, and cousins You can the testing in person or through the mail The more members you test the easier it will be to set up a pedigree Using the symbols defined in Figure make as complete a pedigree of your family as possible for the ability to taste PTC As in Part I, where possible, you should label individuals with their apparent genotype RESULTS, PART II: Your family's pedigree: For an interesting discussion of taste test papers, see Appendix Monday, February 02, 2009 Page 49 6:40:06 PM BIO 114: BIOLOGY OF NONINFECTIOUS DISEASE — LABORATORY MANUAL EXERCISE 6: PEDIGREE ANALYSIS CONCLUSIONS, PART II: Is the ability to taste PTC a genetic trait in your family? If yes then: a Is it dominant or recessive? b Is it sex-linked? You have until 5:00 on the last day of classes to make your pedigree and answer the questions above, for points Monday, February 02, 2009 Page 50 6:40:06 PM ... the laboratory can be handed in today for five points Monday, February 02, 2009 Page 46 6:40 :06 PM BIO 114: BIOLOGY OF NONINFECTIOUS DISEASE — LABORATORY MANUAL EXERCISE 6: PEDIGREE ANALYSIS PEDIGREE. .. NONINFECTIOUS DISEASE — LABORATORY MANUAL EXERCISE 6: PEDIGREE ANALYSIS Figure Key to symbols commonly seen in pedigrees PROCEDURE, PART I: There are four hypothetical pedigrees printed on the... NONINFECTIOUS DISEASE — LABORATORY MANUAL EXERCISE 6: PEDIGREE ANALYSIS PEDIGREE NO 3: Is there a clear pattern of inheritance? If so, is the trait dominant or recessive? Is it sex-linked? PEDIGREE NO 4: