Question

The mutation that causes Huntington disease involves a DNA segment known as a CAG trinucleotide repeat. Normally, the CAG segment is repeated 10 to 35 times within the gene. In people with Huntington disease, the CAG segment is repeated 36 to more than 120 times. The trinucleotide repeat region of the HD gene from six individuals, each of whom has one parent affected by Huntington disease has been amplified by PCR and subjected to gel electrophoresis. The figure shows the bands resulting from this procedure. Complete the statements using the words and phrases on the left (Not all words and phrases are used.) 380 bp 270 bp 220 bp 200 bp #1, #2, #3, and The bands at the top have the trinucleotide repeat regions 44 and #6 The individuals most likely to be affected by the disease are longest Because the length of the repeat region affects disease onset, it is likely that individual will experience earliest onset The individuals least likely to be affected by the disease are shortest #2, #3, and 4