Risk of a very rare disease

[Daurius]

Hello everyone, could you please help me with the following excercise?

A women is a carrier of a mutation for a very rare disease (for instance, an inborn, recessive glycosylation disorder). Her partner is her second cousin (see family tree). What is the risk that the child has this disease ?

1. 1 in 2.

2. 1 in 4.

3. 1 in 16.

4. 1 in 64.

5. 1 in 256.

 

Thank you.