Question

Study the pedigree analysis of Myotonic dystrophy given below:

Answer the following questions:

1. Write genotype of A, B, C and D.
2. Identify whether the trait is
   1. Sex linked or autosomal
   2. Dominant or recessive

Answer 1

1. Writing the Genotype of A, B, C, and D: As an autosomal dominant disorder, myotonic dystrophy requires that afflicted individuals possess a minimum of one dominant allele (D). Those that are unaffected must be homozygous recessive (dd).
   

   Individual	Affected status	Possible genotype
   A (Mother)	Affected	Dd
   B (Father)	Unaffected	dd
   C (Affected Male Child)	Affected	Dd
   D (Unaffected Female Child)	Unaffected	dd

2. Identifying the trait type:
   1. In the first generation, the characteristic is found in about similar amounts in both male and female progeny. This suggests that it is not sex-linked but rather an autosomal condition.
   2. As a feature of dominant inheritance, the condition manifests in all generations. The fact that heterozygous individuals (Dd) are affected indicates that the disease is autosomal dominant.