Question

Huntington's disease (HD) is a late-onset fatal genetic disorder that causes the progressive breakdown of nerve cells in the brain. The disease is caused by an autosomal dominant mutation whereby an expansion of a CAG trinucleotide repeat is observed in the gene Huntingtin (HTT. Where normal individuals have up to 35 copies of the triplet, individuals with repeat regions containing more than 35 repeats are susceptible to HD, and all disease alleles with 42 or more repeats are completely penetrant. In general, a greater number of repeats correlates with a younger age of onset of the disease. The CAG trinucleotide repeat region of HTT in six individuals (A-F) was PCR amplified and analyzed by gel electrophoresis, with the results shown below. The numbers in the right column indicate the sizes of the PCR amplicons in bp. Each of the six individuals has one affected parent HiE 380 bp 270 bp 220 bp 200 bp ABCDE Consider the two PCR primers used to amplify the CAG trinucleotide repeat region. If the 5' 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' end of the other primer could be found? Assume that the diagram shows the largest HD allele possible (Le., 35 CAG repeats). Express your answer using Arabic numerals separated without any punctuation marks or units; e.g, if your answer is "five nucleotides", enter: 5 I

Answer 1

Answer: - It is given that normal individuals have 35 copies of triplets. It means the gene size ; 35x3 = 105bp. - And those individuals which have more than 42 copies of triplates. They are affected by the huntigtons. It means the gene size in abbected individuals is 4223 = 126 bp (8) more than it. - Now huntigton's is also caused by dominant mutation. It means when the individual have either single allele (oh) both alleles are bound to be more than 126 bp, then such individuals have huntigton disease. Now it we look the band pattern it these six individuals you will find that all individuals have gune size of more than 120bp. That's why all sin individuals have huntigton's disease, please rate my Ansuel 4