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Perplexing Pedigree.doc
Perplexing Pedigree.doc
Perplexing Pedigree.doc
Perplexing Pedigree.doc
Perplexing Pedigree.doc
Perplexing Pedigree.doc
Perplexing Pedigree.doc
Perplexing Pedigree.doc
Perplexing Pedigree.doc
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Perplexing Pedigree.doc

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  • 1. Perplexing Pedigrees On the following pedigrees, color the people with the disease red. Color the carriers yellow. 1. In humans hemophilia is a sex-linked recessive trait. Having blood that will clot is normal. XHY XHXh XHXh XHY XHXH XhY 2. In humans, one form of deafness is inherited as an autosomal dominant disease (D) over its recessive normal allele (d). Dd dd Dd Dd dd dd dd DD dd Dd dd dd
  • 2. 3. Ellis-van Creveld syndrome is a rare genetic disorder characterized by short-limb dwarfism, polydactyly (additional fingers or toes), malformation of the bones of the wrist, dystrophy of the fingernails, partial hare-lip, cardiac malformation, and often prenatal eruption of the teeth. It is an autosomal recessive disease. Ee Ee Ee EE ee ee EE ee EE Ee Ee EE 4. Consider the following pedigree for Tay-Sachs, an autosomal recessive disease in humans. Tay-Sachs disease is a fatal genetic disorder in which harmful quantities of a fatty substance called ganglioside GM2 accumulate in the nerve cells in the brain. 1 Write the genotype of each person below their symbol. Use t to represent the allele for Tay-Sachs and T to represent the normal allele. If the genotype cannot be determined indicate the possible genotypes.
  • 3. 5. Examine each pedigree below and determine its most likely pattern of inheritance. Drag the pedigree into the table on the next page and place it in the appropriate cell based on its pattern of inheritance. While there are numerous types of inheritance, for this exercise consider the following four types: Autosomal dominant Autosomal recessive Males & females are equally likely to have the trait. Males & females are equally likely to have the trait. Traits do not generally skip a generation. Traits may be hidden for generations. The trait is expressed if the dominant allele is present. The trait is not expressed if the dominant allele is present. Homozygous or heterozygous individuals have the trait. Only homozygous individuals have the trait. Sex-linked dominant Sex-linked recessive All daughters of a male with the trait will have the The trait is far more common in males than in females. trait. All daughters of a male with the trait are heterozygous There is no male-to-male transmission. carriers. Females with the trait may pass the trait to sons and There is no male-to-male transmission. daughters. Mothers of sons who have the trait are either carriers or have the trait themselves.
  • 4. Autosomal dominant Autosomal recessive Sex-linked dominant Sex-linked recessive
  • 5. Pedigrees I and J are for the same disease. 6. Can the trait shown in pedigree I be autosomal dominant? If you answered "no", explain why by referring to specific individuals that you have marked. 7. Can the trait shown in pedigree I be autosomal recessive? If you answered "no", explain why by referring to specific individuals that you have marked. 8. Can the trait shown in pedigree I be X linked recessive? If you answered "no", explain why by referring to specific individuals that you have marked. 9. Can the trait shown in pedigree I be X linked dominant? If you answered "no", explain why by referring to specific individuals that you have marked.
  • 6. 10. Can the trait shown in pedigree J be autosomal dominant? If you answered "no", explain why by referring to specific individuals that you have marked. 11. Can the trait shown in pedigree J be autosomal recessive? If you answered "no", explain why by referring to specific individuals that you have marked. 12. Can the trait shown in pedigree J be X linked recessive? If you answered "no", explain why by referring to specific individuals that you have marked. 13. Can the trait shown in pedigree J be X linked dominant? If you answered "no", explain why by referring to specific individuals that you have marked. 14. Examine each instance in pedigrees I & J where the trait is passed to offspring. What do you observe about the source of the inherited trait? 15. Mendelian genetics assumes that in all cases each parent contributes equally to the genotype of the offspring. Do the data shown in I & J demonstrate this idea? Why or why not? 16. Consider autosomal dominant & recessive diseases and sex-linked dominant & recessive diseases. Where in the cell is the DNA located that controls these traits?
  • 7. Read the info below from Genetics & Identity. Why is the Y chromosome important? Because the Y chromosome cannot easily swap information with the X chromosome, the Y chromosome in a man's sperm will be an almost exact copy of the Y chromosome in his body's cells. Therefore, any sons the man fathers will also carry this same Y chromosome. Polymorphisms in a man's Y chromosome are also passed directly on to his sons, and then on to their sons and so on. These polymorphisms mark a man's Y chromosome and distinguish it from those of other men. As scientists know approximately how often certain kinds of mutations occur they can look for these and determine how closely related any two men are. The more Y chromosome polymorphisms two men share, the more recently they had a common ancestor. Y chromosomes in men living today thus retain a record of the chromosome's passage through time. They can reveal paternal ancestry and show relationships between different groups of men. What can mitochondrial DNA tell us? It is not just men who retain a record of their genetic ancestry. Women also carry a record of their history in their mitochondrial DNA. This DNA is found outside the cell's nucleus in the mitochondria, which produce the cell's energy. Following fertilization of an egg by a sperm, the sperm's mitochondria are discarded and only the mitochondria from the mother are retained in the new cells. Therefore, the DNA in each person's mitochondria is a unique record of his or her maternal heritage. Like the Y chromosome, mitochondrial DNA can also include polymorphisms. In the same way that scientists study polymorphisms in Y chromosomes, they can use polymorphisms in mitrochondrial DNA to construct extended mother to daughter genealogical trees. 17. Could the inheritance of an allele carried on the Y chromosome explain the inheritance in Pedigrees I & J? Why or why not? 18. Could the inheritance of DNA carried in the mitochondria explain the inheritance in Pedigrees I & J? Why or why not? 19. What new explanation for inheritance comes to light with pedigrees I & J?
  • 8. Summary Autosomal Dominant Conclusions If a child has an autosomal dominant trait, what can you say about the parents? If neither parent has an autosomal dominant trait, what can you say about their children? Autosomal Recessive If two parents have an autosomal recessive trait, what can you say about their children? If two parents do not exhibit an autosomal recessive trait, what can you say about their children? Can autosomal recessive traits skip generations? Sex-linked Recessive What can you conclude about male children of mothers with an X- linked recessive trait? What can you conclude about female children of fathers with an X-linked recessive trait? What can you conclude about male children of fathers with an X-linked recessive trait? How do the number of males with X-linked recessive traits compare with the number of females? (Is it more or less?) Sex-linked Dominant What can you conclude about male children of mothers with an X- linked dominant trait? What can you conclude about female children of fathers with an X-linked dominant trait? What can you conclude about male children of fathers with an X-linked dominant trait?
  • 9. Y chromosome What can you conclude about female children of fathers with a Y- linked trait? What can you conclude about male children of fathers with a Y-linked trait? Mitochondrial DNA What can you conclude about female children of mothers with a mitochondrial trait? What can you conclude about male children of mothers with a mitochondrial trait? What can you conclude about female children of fathers with a mitochondrial trait? What can you conclude about male children of fathers with a mitochondrial trait?

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