Despite the form, statement (b) is not actually a logical conjunction. It is a statement about the collective of both parents.
This becomes clearer if we strengthen the statement slightly to “Alvin’s mother and father are responsible for all of his genome”. It’s much more clear now that it is not a logical conjunction. If it were, it would mean “Alvin’s mother is responsible for all of his genome and Alvin’s father is responsible for all of his genome”, both of which are false.
This is probably meant as a reply to this comment.