How to Analyze Autosomal Recessive Pedigree Trait?

In order to analyze this pedigree, we have to first check whether it is dominant or recessive in nature.

The criteria for dominant pedigree trait is:

a. There should not be skipping of generation
b. Either or both the parents should be affected to pass a disease to the next generation. 

Note: when two normal parents transfer a disease to the offspring, it is a recessive characteristic.

Now, when you see the above pedigree, you can see that in the second generation, two parents 8 and 9 are normal, but passing a disease to their daughter (17) in the third generation. So, you can say that the pedigree is recessive.

The second step is to check whether it is autosomal recessive or X-linked recessive. The best way is to first check for X-linked. If it is X-linked, it should follow two conditions:

a. More boys affected than girls
b. Affected mom passes the disease to all her sons

You can see that in the first generation, an affected mom does not pass disease to all her sons, so, it is not an X-linked trait.

So, we can conclude that the above pedigree shows autosomal recessive trait.