Pedigree analysis of a Y-linked trait

Y-linked traits never occur in females, and occur in all male descendants of an affected male.

The concepts of dominant and recessive do not apply to Y-linked traits, as only one allele (on the Y) is ever present in any one (male) individual.
Males with a single Y- or X-linked allele are described as hemizygotes, because only one allele is present.

Homework: Write out the genotypes of every individual in the tree.

Figure ©2002 by Griffiths et al;. all text material ©2012 by Steven M. Carr