I am struggling with genetics.
I am struggling with genetics.
I am struggling with genetics.
I am struggling with genetics.
I am struggling with genetics.
I am struggling with genetics.
I am struggling with genetics.

Pedigree analysis.

Can somebody answer me why the above diagram is a X linked recessive mode?

It is because the grandparents, one of them is with the disease, therefore the genotype of the grandfather is homozygous, that means XaY. Then for the grandmother, she is not diseased, therefore her genotype is XAXa or XAXA, which makes her heterozygous?

Then for the F1 generation, all are not affected... because x linked recessive would only show in the phenotype if there are two homozygous genotype?

They have 2 daughters, and they both inherited a X from mum and another X from dad. However dad is diseased, the daughters would not show the phenotype because it would only be shown if the genotypes are homozygous.

For the F2 generation, one boy is infected with the disease. That means that his genotype is XaY. Taking the normal outsider rule, the guy who marry the diseased girl is homozygous, which means that he is normal. XAY is his genotype?

That determines his mum's genotype. His father would not have passed the disease to him, unless it is Y linked because only guys have an Y. Since the father is perfectly normal, than the mum must be the carrier for the disease, and therefore pass one Xa to the son, and the son showed it in his phenotype.