Yes. Easy/hard? Try this next one…
Explanation: The grandparents are blood group A and AB. For the grandmother, you can’t immediately identify if they are AA or AO (or maybe you can…). What you can say is that the mother of the unknown person definitely has one A from their father but, because A is dominant we can’t know if they got another A from the grandmother or an O. So, either AA or AO, crossing with an OO person means the offspring could either be AO (A blood group) or OO (O blood group).
Same pedigree… now updated with the known phenotype of the last person, turns out they were O. Can we do another?
We are going to look at the person indicated by the arrow again.
Their father has been genotyped and is BO. What are the relative probabilities of the different potential phenotypes of the person indicated by the arrow? [You might need to write this one down…I did say we would get more difficult!]