How to Analyze X-linked Recessive Pedigree Trait?

We will analyze the pedigree based on the above diagram.

The very first thing we need to know is whether the pedigree chart is recessive or not. We know that for recessive trait, it should fulfill two basic conditions:
a. There must be skipping of generation
b. Two normal parents have affected offspring

Now, when we look at the pedigree, the first condition is not fulfilled, as there is no skipping of generation, however, the second situation is fulfilled as we can see in the second generation where two unaffected parents have affected offspring in the third generation. So, the mode of inheritance is recessive.

The second condition is whether it is X-linked recessive or not. So, for X-linked recessive condition, there are few conditions as well.
a. More boys are affected
b. Affected mom has to have all affected sons.

Now when we see the pedigree chart above, we can see that more boys are affected than girls. Besides, affected mom has got all affected sons. So, we can say that the above pedigree is X-linked recessive.

Note: When you analyze a pedigree, always look for X-linked trait first because it is easy to determine compare to autosomal traits.