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: Pathology
Myotonic dystrophy is inherited in chromosomes 
Select and explain. 
A. 21, B. 20, C. 19, D. 24
C: 19
Answer: C: 19 
Explanation: Ans. is 'c' i.e., 19 o Myotonic dystrophy is associated with a trinucleotide CTG repeat expansion on chromosome 9. o This expansion affects the mRNA for the dystrophila myotonia protein kinase (DMPK). Myotonic dystrophy' o The characteristic feature of myotonic dystrophy is myotonia, i.e., the sustained involuntary contraction of group of muscles. o Of all the dysdrophies, only myotonic dystrophy shows pathological changes in the intrafusal fibres of the muscle spindles. o Extra-muscular abnormalities are : - Cataract Frontal baldness Gonadal atrophy o DM Dementia Decreased IgG