This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
Gene for myotonic dystrophy is coded on chromosome number : 
Select and explain. 
A. 19, B. 20, C. 21, D. 24
A: 19
Answer: A: 19 
Explanation: Answer is A (Chromosome 19) : 359. The disorder is transmitted by a mutation in an 'unstable trinucleotide repeat sequence' in a gene at 19q 133. Myotonia Dystrophica : It is the most common adult muscular dystrophy.Q Myotonic dystrophy is an autosomal dominant disorder. Q The disorder is transmitted by a mutation in an 'unstable trinucleotide repeat sequence' in a gene at 19q 133 Muscle atrophy selectively involves type I fibres only. Q (in 50% of cases) Myopathy in Myotonia is unique in the sense that it is typically distal in contrast to other myopathies which are mostly proximal. Q Myotonia usually appears by the age of 5 years Q,and causes a slow relaxation of hand grip following a forced voluntary closure.