Some of the possible genotypes for the parents of a child with dwarfism is a RR mother, and a RR father, then 100 percent of their children will have dwarfism. If a both of the parents are Rr then 75 percent of their children will have dwarfism. If one parent is RR and the other parent if Rr then all of their children will have dwarfism. Also if the mom is Rr and then dad is rr then at least 50 percent of of their children will have dwarfism. The abnormality of dwarfism is a faulty allele, a mutation in the growth factor in gene 3. The mutation is also called FGFR3.
This isn't actually correct with achondroplasia because a RR, as you call it, genotype is typically lethal. Nearly (only because I hate to say always) every person with achondroplasia is Rr. That means that there is a 50% chance to have an achondroplastic child, 25% chance that they will not, and 25% chance that the child will inherit RR and wont survive.
ReplyDeleteIf one parent has achondroplasia (Rr) and the other does not (rr), then the odds are still 50% to have a child with achondroplasia, but now 50% to have a child without it, and 0% chance to the lethal form.
None of this stuff is lethal they either get achondroplasia or they don't. RR just means that they will most likely have achondroplasia. rr means that you have a really good chance that the person will not get it.
ReplyDeleteRR is referred to as having a double Dominance of the dwarfism gene. There are only a handful of successful RR cases because the majority of them die within days of being born.
DeleteRR is fatal in utero or shortly after birth. a parent with achondroplasia will be Rr.
ReplyDelete