What type of inheritance is shown by this pedigree?

1^st generation - Male is affected in this pedigree while female is normal.

2^nd generation – Male and female both are normal.

3^rd generation – One male is affected while the other male is normal. Both the females are normal.

The given pedigree shows X-linked inheirtance.

An X-linked trait is carried on the X chromosome. In pedigrees depicting X-linked inheritance, usually only males are affected and, although affected males may occur in consecutive generations, transmission is always through females. This is based on the fact that males have a single X chromosome (in addition to their Y chromosome), which they always inherit from their mother and will always pass on to their daughters but never to their sons. Females, on the other hand, have two X chromosomes. Therefore, they can be carriers of an X-linked mutation, but in most cases are phenotypically unaffected because they have a second (nonmutated) X chromosome, compensating for whatever loss of function is caused by the mutated gene.