Diabetes mellitus is defined as a state of permanent hyperglycemia

Diabetes mellitus is defined as a state of permanent hyperglycemia. Some forms of diabetes mellitus are due to a malfunction of the gene coding for insulin and are therefore hereditary. Here is the family tree of a family with members who have diabetes mellitus.

a) Specify whether the allele responsible for the disease is dominant or recessive. Justify the answer.

b) Specify if the allele is carried by an autosome or by a sex chromosome. Justify the answer.
Sorry the picture is in french 

homme atteint= male carrier 

homme non atteint= non carrier male

femme non atteint= non carrer female

femme atteinte= female carrier