Er dette korrekt?

(a) The mode of inheritance can be X-linked recessive or autosomal recessive. But if there is only one answer for this, I'd choose X-linked.

Why recessive?
- If it is dominant, then every generation will have at least one individual expressing the disorder.
- If it is dominant, then normal parents cannot produce offspring with the disorder.
So dominant is ruled out. It is recessive.

Why X-linked?
- Notice that those affected are males. If it is autosomal, males and females should have equal probability of inheriting the disorder. BUT since the number of individual is quite small, it is also likely that autosomal recessive inheritance gives the same observation.
- If it is autosomal, then look at my answer in (b), how many people must carry a mutant allele in order to get such a pedigree? That's a lot. II-2 and III-1 are "outsider" (can't think of a more suitable word), so chances are they will not have the mutant allele. But, again, this is not totally impossible, it is just that the chances are slightly lower.

(b) I will give you the genotypes for both when the mode of inheritance is X-linked recessive and the mode of inheritance is autosomal recessive.

If it is X-linked recessive (I use A and a instead X and x to avoid confusion),
I-1 is aX Y
I-2 can be AX aX or AX AX
II-1 is AX aX
II-2 is AX Y
III-1 is AX Y
III-2 is AX aX
III-3 is aX Y
III-4 is aX Y
IV-1 is aX Y
IV-2 is aX Y
IV-3 can be AX aX or AX AX

If it is autosomal recessive (here I can use X and x),
I-1 is xx
I-2 is Xx
II-1 is Xx
II-2 is Xx
III-1 is Xx
III-2 is Xx
III-3 is xx
III-4 is xx
IV-1 is xx
IV-2 is xx
IV-3 is Xx