Final answer:
The statement that Rh- individuals must have parents who are both Rh- is FALSE. While Rh- can have an Rh+ parent with both alleles, Rh- cannot exclusively have Rh- parents, and Rh+ offspring are possible from an Rh- individual if the other parent is heterozygous for the Rh factor. Hemolytic disease of the newborn occurs in subsequent pregnancies because the first pregnancy sensitizes the Rh- mother to Rh+ cells.
Step-by-step explanation:
Under normal Mendelian inheritance, the statement 'Rh- individuals must have parents who are both Rh-' is FALSE. While it's true that Rh- individuals can only pass on the recessive Rh- allele, an Rh- individual can have one parent who is Rh+ as long as that parent is heterozygous for the trait (carrying both Rh+ and Rh- alleles).
An Rh+ individual can indeed have offspring with Rh- blood if they are heterozygous (Rh+Rh-), and their partner contributes an Rh- allele. Furthermore, an Rh+ individual must have at least one Rh+ parent, as the Rh+ allele is dominant. It is also false to assert that Rh- individuals cannot have offspring with Rh+ blood; if an Rh- parent mates with an Rh+ individual who is heterozygous for the Rh factor, there is a possibility for Rh+ offspring due to the dominant nature of the Rh+ allele.
Hemolytic disease of the newborn becomes a problem during the second or subsequent pregnancies with an Rh+ fetus because the first pregnancy sensitizes the Rh- mother, leading to the production of IgG antibodies which can cross the placenta in later pregnancies and attack the Rh+ fetus's red blood cells, causing anemia.