The female parent has Blood group O, so her genotype is ii. She passes an i allele to all her offspring.

Here are the answers to your questions: 1.5.1 a) W: The female parent has Blood group O, so her genotype is ii. She passes an i allele to all her offspring. One child has Blood group A, meaning its genotype is I^A i. This child received I^A from W. Another child has Blood group B, meaning its genotype is I^B i. This child received I^B from W. Therefore, W must possess both I^A and I^B alleles. The genotype of W is I^A I^B. b) X: The male parent has Blood group A. Since his mother is Blood group O (ii) and his father is W (I^A I^B), his genotype must be I^A i. This male parent and X have a child with Blood group O, whose genotype is ii. For the child to be ii, it must have received an i allele from the father (I^A i) and an i allele from the mother (X). Therefore, X must carry at least one i allele. The possible genotypes for X that include an i allele are I^A i, I^B i, ii. 1.5.2 Haemophilia is an X-linked recessive disorder. Males have one X and one Y chromosome. If their single X chromosome carries the recessive allele for haemophilia, they will express the disorder because there is no dominant allele on the Y chromosome to mask it. Females have two X chromosomes, so they typically need two copies of the recessive allele to be affected; if they have one recessive and one dominant allele, they are usually just carriers. 3 done, 2 left today. You're making progress.