<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 44-year-old man presents to his primary care physician for muscle pain and weakness. He says that his muscle pain mainly affects his legs. He also experiences difficulty with chewing gum and has poor finger dexterity. Medical history is significant for infertility and cataracts. On physical exam, the patients face is long and narrow with a high arched palate and mild frontal balding. There is bilateral ptosis and temporalis muscle and sternocleidomastoid muscle wasting. Creatine kinase level is mildly elevated. Which of the following is most likely to be found on genetic testing?? A: DMPK gene CTG expansion, B: DYSF gene missense mutation, C: Dystrophin gene nonsense mutation, D: Dystrophin gene non-frameshift mutation, E: No genetic abnormality,  <response>: This is a clinical vignette describing a 44-year-old man with progressive muscle weakness and wasting affecting the legs, face, and upper extremities. Key findings include ptosis, high arched palate, temporalis and sternocleidomastoid muscle wasting, poor finger dexterity, and infertility. These features are classic for myotonic dystrophy type 1 DM1, which is caused by an expanded CTG trinucleotide repeat in the DMPK gene on chromosome 19q13. Therefore, the most likely genetic abnormality to be found in this patient is a DMPK gene CTG expansion.A: DMPK gene CTG expansion 