The trinucleotide repeat region of the Huntington disease locus $(H D)$ in six individuals is amplified by PCR and analyzed by gel electrophoresis as shown in the following figure; the numbers to the right indicate the sizes of the PCR products in be. Each person whose DNA was analyzed has one affected parent. a. Which individuals are most likely to be affected by Huntington disease, and in which of these people is the onset of the disease likely to be earliest? b. Which individuals are least likely to be affected by the disease? c. Consider the two PCR primers used to amplify the trinucleotide repeat region. If the $5^{\prime}$ end of one of these primers is located 70 nucleotides upstream of the first CAG repeat, what is the maximum distance downstream of the last CAG repeat at which the $5^{\prime}$ end of the other primer could be found? [Assume that the diagram shows the largest $H D^{+}$ allele possible (that is, 35 CAG repeats).
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The individuals most likely to be affected by Huntington disease are those with the longest trinucleotide repeat regions, as the length of this region is correlated with the severity of the disease. In this case, individuals 2, 3, and 6 have the longest repeat Show more…
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The trinucleotide repeat region of the Huntington disease locus (HD) in six individuals is amplified by PCR and analyzed by gel electrophoresis as shown in the following figure; the numbers to the right indicate the sizes of the PCR products in bp. Each person whose DNA was analyzed has one affected parent. A) Which individuals are most likely to be affected by Huntington disease, and in which of these people is the onset of the disease likely to be earliest? B) Which individuals are least likely to be affected by the disease?
Madhur L.
Md.Daniyal A.
3. Primer Design You are analyzing the region of DNA shown below to determine how many AATG repeats are present. To do so, you must amplify the entire region of AATG repeats. Design primers of 16 bases each so they anneal outside the region of interest. More than one primer pair is possible, but just give one. 5′-ACTGGCACAGAACAGGCACTTAGGAATGAATGAATGAATGAATGAATGAATGACCTGTGTGGTTCCCAGTTCCTCC-3′ 3′-TGACCGTGTCTTGTCCGTGAATCCTTACTTACTTACTTACTTACTTACTTACTGGACACACCAAGGGTCAAGGAGG-5′ a. Primer 1: Primer 2: b. Highlight the repeats in yellow. c. How many repeats of the AATG sequence are there? 4. PCR Product size You use the primers below in a PCR with the DNA in question 3 above. 5'-CTGGCACAGAACAGGCACTT -3' and 3'-ACACACCAAGGGTCAAGGAG -5' a. How long (in base pairs) will the PCR product be? b. How long would the PCR product be if there were 5 repeats? What about if there were 10 repeats?
Josee P.
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