The following is a pedigree that shows the inheritance of a rare completely pene
ID: 40524 • Letter: T
Question
The following is a pedigree that shows the inheritance of a rare completely penetrant autosomal dominant disorder. DNA samples from generations I, II, III and IV were obtained and subjected to RFLP analysis. The results of the analysis are shown below. The RFLP marker used for the top panel is marker #135, and the one used for the bottom panel is marker #219, both in chromosome 17.
Question 1:
D) Could you use RFLP analysis with the markers shown above to help determine the probability that the child will have the disorder? Which RFLP marker would you choose to analyze the DNA from the fetus for prenatal screening? How would you determine the odds of the child having the disease based on the RFLP results? Explain in detail.
The following is a pedigree that shows the inheritance of a rare completely penetrant autosomal dominant disorder. DNA samples from generations I, II, III and IV were obtained and subjected to RFLP analysis. The results of the analysis are shown below. The RFLP marker used for the top panel is marker #135, and the one used for the bottom panel is marker #219, both in chromosome 17. Question 1: D) Could you use RFLP analysis with the markers shown above to help determine the probability that the child will have the disorder? Which RFLP marker would you choose to analyze the DNA from the fetus for prenatal screening? How would you determine the odds of the child having the disease based on the RFLP results? Explain in detail.Explanation / Answer
RFLP can be used to analyse the disorder of the child.
If a particular RFLP is usually associated with a particular genetic disease, then the presence or absence of that RFLP can be used to counsel people about their risk of developing or transmitting the disease. The assumption is that the gene they are really interested in is located so close to the RFLP that the presence of the RFLP can serve as a surrogate for the disease gene itself. But people wanting to be tested cannot simply walk in off the street. Because of crossing over, a particular RFLP might be associated with the mutant gene in some people, with its healthy allele in others. Thus it is essential to examine not only the patient but as many members of the patient's family as possible.
The most useful probes for such analysis bind to a unique sequence of DNA; that is, a sequence occurring at only one place in the genome. Often this DNA is of unknown, if any, function. This can actually be helpful as this DNA has been freer to mutate without harm to the owner. The probe will hybridize (bind to) different lengths of digested DNA in different people depending on where the enzyme cutting sites are that each person has inherited. Thus a large variety of alleles (polymorphisms) may be present in the population. Some people will be homozygous and reveal a single band; others (e.g., all the family members shown below) will be heterozygous with each allele producing its band.
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