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Genetics/DNA Problems

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You are studying a human disease that is inherited in an autosomal dominant
fashion. You recognize that the disease maps to chromosome 10, so you obtain four DNA probes that hybridize to different chromosome 10 regions. A family in which the disease appears presents itself to a medical genetics clinic. DNA is extracted from each family member shown, cut with a restriction enzyme and tested on a Southern blot with each probe.

1a) Which probe would be most useful for your studies and for genetic counseling? Explain.

1b) Does the DNA probe that you selected in part a) actually include the disease gene? Explain.

1c) What is unusual about individual #7? What is the most likely explanation? Hint: Think outside the box.

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RESTRICTION FRAGMENT LENGTH POLYMORPHISMS (RFLPs) and PEDIGREE ANALYSIS

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Question: You are studying a human disease that is inherited in an autosomal dominant fashion. You recognize that the disease maps to chromosome 10, so you obtain four DNA probes that hybridize to different chromosome 10 regions. A family in which the disease appears presents itself to a medical genetics clinic. DNA is extracted from each family member shown, cut with a restriction enzyme and tested on a Southern blot with each probe. (See figure on next page. Filled symbols indicate affected individuals).

1a) Which probe would be most useful for your studies and for genetic counseling? Explain.

Restriction fragment length polymorphisms (RFLPs) are a very important genetic tool for assessing or predicting disease state in organisms. Everyone's DNA differs slightly from everyone else's DNA. It is these random variations that allow for the useful tool known as RFLPs. These variations are called alleles (different forms of a given gene). If a restriction enzyme (which cleaves DNA at specific endonucleolytic sites) is known to exist which cuts the DNA right at the locus for the alleles in question then we have the possibility that different restriction fragment lengths will be predictive of the existence or absence of the given allele.

If you need to brush up on RFLPs, here are a few useful sites:
http://home.comcast.net/~john.kimball1/BiologyPages/R/RFLPs.html
http://www.bio.davidson.edu/COURSES/genomics/method/RFLP.html
http://www.accessexcellence.org/RC/AB/BC/How_RFLPs_Find.html

The best probes are those that highlight or show restriction fragments of variable length. Useless ...

Solution Summary

Human diseases which are inherited in an autosomal dominant fashion are analyzed. DNA extracted from each family member are determined.

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