On the pedigree, the square indicates that the individual is male and the circle indicates that the individual is female.
White shapes indicate that the individuals are not affected by a determined trait.
The shaded shapes indicate that the individuals are affected by the trait.
If you look at the pedigree, on the first generation on the left, and unaffected male and an affected female were crossed, the resulting offspring was an unaffected male.
Let's assume that the trait is autosomal recessive, the letter "A" is the dominant allele and the letter "a" is the recessive allele, you can represent this pedigree as follows:
The mother was affected by the trait but the child wasn't, since she only has two identical alleles to pass, it is most likely that the trait is recessive.
Also, the trait can be considered autosomal, if it was a sex-linked trait associated with the X-chromosome, and consider that males have only one X-chromosome inherited from their mother then the child should also express the trait.
If you look at the second and third generations, the crossing of two apparent unaffected individuals produced 6 offspring, two of which are affected by the trait one male and one female. This fact also suggests that the trait is recessive, both individuals in the second generation can be considered heterozygous. The trait is autosomal because the affected individuals in the third generation have different genders.
