A part of an mRNA has the base sequence GCA. Which change to this sequence would indicate a missense mutation?

A. GCC
B. GCU
C. GCG
D. GAA

If two parents who's blood types are both b produce a child that has blood type o, what can you say about the parent's genotybes? oa) one is ii ob) one is ibi oc) both are bi od) nothing, this is impossible