Pedigree Analysis - PC\|MAC



|Pedigree Analysis- Annotate the following informational text on pedigree. Use the symbols we have been utilizing this semester to annotate. Pull out 4 |

|important points from the text and summarize them in the margins as well. |

|What is it ? |

|A pedigree is a diagram of family relationships that uses symbols to represent people and lines to represent genetic relationships. These diagrams make |

|it easier to visualize relationships within families, particularly large extended families. Pedigrees are often used to determine the mode of |

|inheritance (dominant, recessive, etc.) of genetic diseases. A sample pedigree is below. |

|[pic] |

|How is it organized? |

|squares represent males |

|circles represent females. |

|Horizontal lines connecting a male and female represent mating. |

|Vertical lines extending downward from a couple represent their children. Subsequent generations are therefore written underneath the parental |

|generations and the oldest individuals are found at the top of the pedigree. |

|If the purpose of a pedigree is to analyze the pattern of inheritance of a particular trait, it is customary to shade in the symbol of all individuals |

|that possess this trait In the pedigree above, the grandparents had two children, a son and a daughter. The son had the trait in question. One of his |

|four children also had the trait. |

|Active Notes/ Cornell Style:- Create 5 questions that can be answers by reading the above selection. Write the questions on the left and answers on the|

|right. |

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|In the exercises below, assume that the trait in question is a genetic disease or abnormality. We will learn patterns of inheritance that have the |

|following modes of inheritance: |

|autosomal dominant |

|autosomal recessive |

|X-linked recessive |

|Developing Conclusions About Different Modes of Inheritance |

|Autosomal Dominant? Autosomal Recessive? |

|Answers Answers |

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|X-Linked Recessive? |

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|MAKING A PEDIGREE CHART |

|Now, follow the story, and make the appropriate pedigree chart. |

|This is the story of Grandma and Grandpa Flipnob, and their clan! They were married way back in 1933, and have been just like newlyweds ever since. From|

|their union, 4 individuals were created. Elizabeth, the eldest, was born in 1935. Fred soon followed in 1936. In 1939 Michelle was brought into this |

|world. Mickey (a surprise to the whole family was the baby of the family, not being born until 1950. |

|Elizabeth fell in love at a young age, and wed her high school sweetheart, David, in 1954. From this marriage, two bundles of joy came about (at the |

|same time): |

|John and Sonny - 1955 (twins)! |

|It took Fred a little longer to find his soul mate. Finally in 1970, Fred found the woman of his dreams, Wilma, and they were married. Since they |

|married so late in life, they only brought one new person into this world: |

|Barney - 1972 |

|Michelle was a hard working woman, and never found time in her schedule for love. She led a very productive and fulfilling life, but she never did marry|

|and have children. |

|Mickey was a wild one!! After a long string of girlfriends, he finally chose Monica to spend the rest of his life with. They were wed in 1975 and |

|brought two girls into this world: |

|Krista - 1977 |

|Janet - 1979 |

|Answer the following questions regarding your pedigree: |

|1. Who are the inlaws? |

|[pic] |

|2. What is the relationship between the people in the third generation? |

|[pic] |

|Now that you have your pedigree chart together, shade the appropriate circles and squared from the information to follow. Remember that individuals who |

|possess the RECESSIVE trait are to be filled in. Those individuals not filled in possess at least one dominant trait. |

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|Dominant/Recessive Inheritance - Freckles |

|Not having freckles is a recessive trait. |

|Grandpa Flipnob did not have freckles, but his beautiful bride did. |

|Fred and Michelle were the only two of their siblings to have freckles. |

|Of the grandchildren, the twins did not have freckles, and neither did Barney, but the two girls did. |

|Now: Using the guide provided, determine the genotypes of all individuals in this pedigree chart for freckles. Remember, having no freckles is a |

|RECESSIVE trait. |

|GUIDE |

|STEP 1 |

|Assign two recessive genes to any person on the pedigree whose symbol is shaded. Small letters are written below the persons symbol. |

|STEP 2 |

|Assign one dominant gene to any person on the pedigree whose symbol is unshaded. A capital letter is written below the persons symbol. |

|STEP 3 |

|Use the information given to you to determine the second alleles for each person with the dominant phenotype. |

|Example: We know that Grandpa Flipnob does not have freckles. If Grandma were BB, could any bb children be produced from Grandma and Grandpa? If Grandma|

|were Bb, could any bb children be produced from them? Do Punnett squares below to determine your answer. |

|From your results, what is Grandma s genotype? ____________________ |

|What must be the genotypes of their children? ____________ ____________ |

|(2nd generation) |

|Fill in these genotypes (along with Grandpa s) beside the appropriate circles and squares. |

|Complete this process until the entire pedigree is completed. |

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|Sex-Linked Inheritance - Colorblindness |

|To complete this part of the activity, you will need to make a copy of your pedigree chart. There is no guide to go along with this section. Just |

|remember to determine the genotypes of those possessing the sex-linked trait first. From there, using Punnett squares, you should be able to determine |

|the genotypes of most, if not all of the family. |

|Neither Grandma or Grandpa Flipnob are colourblind. |

|All of their children have normal colour vision, except for Mickey. |

|Of the grandchildren, the twins both inherited colourblindness, as did their cousins, Barney and Janet. |

|There still remains one colourblind person in this clan, however, that is up to you to determine who. |

|What are the genotypes of the individuals in the Flipnob family for colourblindness? |

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|In the exercises below, assume that the trait in question is a genetic disease or abnormality. We will learn patterns of inheritance that have the |

|following modes of inheritance: |

|autosomal dominant |

|autosomal recessive |

|X-linked recessive |

|Developing Conclusions About Different Modes of Inheritance |

|Autosomal Dominant |

|1. The pedigree below is for a genetic disease or abnormality. We do not yet know if it is dominant or recessive. We will determine if it is possible |

|that the trait is autosomal dominant. If the trait were dominant, we would use the following designations: |

|A = the trait (a genetic disease or abnormality, dominant) |

|a = normal (recessive) |

|If the trait were recessive, we would use the following designations: |

|A = normal (dominant) |

|a = the trait (a genetic disease or abnormality, recessive) |

|a) Assume for the moment that the trait is dominant (we don't know yet). The pedigree shows that three of the individuals have the recessive (normal) |

|phenotype and one individual has the dominant (abnormal) phenotype. Write the genotype of the affected (abnormal) individual next to her symbol in the |

|pedigree below. If you only know one of the genes (letters), use a  "?" for the unknown letter. If possible, write the genotype of the three recessive |

|individuals next to their symbols. As you attempt to write the genotypes, keep in mind that the pedigree may not be possible for a dominant trait; it |

|may not be possible to write the genotypes. |

|[pic] |

|b) Is it possible that the pedigree above is for an autosomal dominant trait? |

|c) Write the genotypes next to the symbol for each person in the pedigree below assuming that it is for a dominant trait.  |

|[pic] |

|d) Is it possible that this pedigree is for an autosomal dominant trait |

|e) What can you conclude from these two examples about the parents of a child that has a dominant characteristic? Put your answer to this question in |

|the summary table (item #1) in the answer sheet. |

|2. We will determine if the pedigree below can be for a trait that is autosomal dominant. Use "A" and "a" as you did for the pedigrees above. |

|a) Write the genotype of each individual next to the symbol. |

|[pic] |

|b) Is it possible that this pedigree is for an autosomal dominant trait? |

|c) In conclusion, can two individuals that have an autosomal dominant trait have unaffected children? Put your answer to this question in the summary |

|table (item #2) in the answer sheet. |

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|Autosomal Recessive |

|3. We will determine if the pedigree below can be for a trait that is autosomal recessive. Use the following designations: |

|A = normal |

|a = the trait (a genetic disease or abnormality) |

|a) Assuming that the trait is recessive, write the genotype of each individual next to the symbol. |

|[pic] |

|b) Is it possible that the pedigree above is for an autosomal recessive trait? |

|c) Assuming that the pedigree below is for a recessive trait, write the genotype next to the symbol for each person. |

|[pic] |

|d) Is it possible that this pedigree is for an autosomal recessive trait? |

|e) If a trait is autosomal recessive, what can you conclude about the children if both parents are affected? Put your answer to this question in the |

|summary table (item #3) in the answer sheet. |

|4. We will determine if the pedigree below can be for a trait that is autosomal recessive. Use "A" and "a" as you did for the previous example. |

|a) Write the genotype of each individual next to the symbol. |

|[pic] |

|b) Is it possible that this pedigree is for an autosomal recessive trait? |

|c) If a trait is autosomal recessive, what can you conclude about the children of two parents that are not affected? Put your answer to this question in|

|the summary table (item #4) in the answer sheet. |

|5. We will determine if the pedigree below can be for a trait that is autosomal recessive. |

|a) Write the genotype of each individual next to the symbol. |

|[pic] |

|b) Is it possible that this pedigree is for an autosomal recessive trait? |

|c) In this pedigree, two generations have been skipped. What can you conclude about recessive traits skipping generations (is it possible or not)? Put |

|your answer to this question in the summary table (item #5) in the answer sheet. |

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|X-Linked Recessive |

|The conclusions that you made for autosomal recessive traits apply to X-linked traits. In this exercise, we will work on some additional conclusions |

|because males have only one X chromosome and females have two. |

|6. We will determine if the pedigrees below can be for a trait that is X-linked recessive. Use the following designations: |

|XA = normal |

|Xa = the trait (a genetic disease or abnormality) |

|Y = Y chromosome (males only) |

|a) Write the genotype of each individual next to the symbol. |

|[pic] |

|b) Is it possible that the pedigree above is  for an X-linked recessive trait? |

|c) Write the genotype next to the symbol for each person in the pedigree below. |

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|d) Is it possible that this pedigree is for an X-linked recessive trait? |

|e) Write the genotype next to the symbol for each person in the pedigree below. |

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|f) Is it possible that this pedigree is for an X-linked recessive trait? |

|g) Write the genotype next to the symbol for each person in the pedigree below. |

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|h) Is it possible that this pedigree is for an X-linked recessive trait? |

|i) What can you conclude about the children of mothers affected with an X-linked recessive characteristic? Put your answer to this question in the |

|summary table (item #6) in the answer sheet. |

|7. We will determine if the pedigree below can be for a trait that is X-linked recessive. We will continue to use the designations "XA and Xa". |

|a) Write the genotype of each individual next to the symbol. |

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|b) Is it possible that this pedigree is for an X-linked recessive trait? |

|c) Which parent did the son get the Xa gene from? |

|d) What can you conclude about father-to-son transmission of X-linked traits? Put your answer to this question in the summary table (item #7) in the |

|answer sheet. |

|8. We will determine if the pedigree below can be for a trait that is X-linked recessive. |

|a) Write the genotype of each individual next to the symbol. |

|[pic] |

|b) Is it possible that this pedigree is for an X-linked recessive trait? |

|c) What can you conclude about the children if both parents are affected with an X-linked recessive trait? |

| d) How does this conclusion compare with the one you made earlier if about both parents being affected by an autosomal recessive trait? |

| e) Do the conclusions that you made for autosomal recessive traits apply to X-linked recessive traits? Put your answer to this question in the summary |

|table (item #8) in the answer sheet. |

|  9a. If a genetic disease is X-linked recessive, what is the phenotype of a female that has only one disease allele (Xa)? |

|b. What is the phenotype of a male with one disease allele? |

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|c. What can you conclude about the number of males that would have the disease compared to the number of females? Put your answer to this question in |

|the summary table (item #9) below. |

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|Application of Pedigree Analysis |

|The conclusions about inheritance (above) can be used to help analyze pedigrees. For each pedigree below, tell if the trait can be autosomal dominant, |

|autosomal recessive, and X-linked recessive. If the pedigree cannot fit a mode of inheritance, tell why.  |

|Pedigree A |

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|Pedigree B |

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|Questions 10 through 15- enter either "yes" or "no" in the table below. |

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|Pedigree A |

|Pedigree B |

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|Autosomal dominant? |

|10) |

|11) |

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|Autosomal recessive? |

|12) |

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|X-linked recessive? |

|14) |

|15) |

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|For each "no" in the table above, explain why or why not below. In your answers, refer to specific individuals in the pedigree by number. |

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|Pedigree A |

|Pedigree B |

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|Autosomal dominant |

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|Autosomal recessive |

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|X-linked recessive |

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