![]() Your parents were carriers for the Rh- blood type. Just like you, these folks with red hair or blue eyes had parents who were carriers for a recessive trait. This is why red hair or blue eyes can seemingly pop up out of nowhere, too. ![]() This is one of the ways that scrambled (or recessive) versions of a gene can remain hidden in a family tree, waiting for a chance to pair up with another recessive version - so they can be seen. If there were no Rh- grandparents, then as I said, at least one grandparent on each side needs to be a carrier. The only possibility that would be harder to explain is if both grandparents were Rh. Your grandparents could have been carriers or maybe one was Rh. Now as I said, there are lots of possibilities here. This is the easiest and by far the most common way for your parents to have each inherited an RHD- gene. In other words, at least one grandparent from dad's side of the family was a carrier. But we DO know that both sets of your grandparents most likely had to have at least one 'scrambled' version of the RHD gene. Well, there are lots of possibilities so we can't tell for sure. Now what about your grandparents? Can we figure out their Rh status from what we know of you and your parents? So you had a 1 in 4 chance of ending up Rh. Mom had a 50-50 shot of passing her Rh- down to you. They had one copy of the RH+ version and one copy of the RH- version. ![]() So, to end up Rh-, BOTH of your Rh+ parents have to be CARRIERS for the Rh- version of the RHD gene. Like nearly everyone else, you have two copies of RHD - one from your mom and one from your dad. But they still have an RH- version they can pass on to their kids. This is because people with just one working copy of the RHD gene make enough RHD protein to be Rh+. As you might have guessed, Rh+ people need just one working RHD gene. So Rh- people make no RHD protein because both versions of their RHD gene don't work. RHD- (or "-") versions are either missing some of the instructions or have them scrambled up. The RHD+ (or "+") version of the gene contains a complete set of the instructions to make the RHD protein. And we know we can live without it because some people do not make any RHD protein. We don't know what this protein does but it sits on the outside of our red blood cells. They carry our oxygen, help us to see, provide support for our cells, etc. Remember, genes are just recipes for making proteins. But what happens if you have one of each? And if we have two RHD- versions, we have Rh- (or "-") blood. Now, it is obvious what happens if we have two RHD+ versions, we have Rh+ (or "+") blood. Together these versions lead to the Rh+ and Rh- that is reported in blood type. One version is called positive and the other negative. ![]() And our genes come in different versions.įor example, there is a gene called RHD that comes in at least two versions. Remember, we all have 2 copies of most of our genes, one from mom and one from dad. Let's use blood type to explain what a carrier is. So, how did you end up with a negative blood type when your folks were positive? Most likely because your parents are carriers for the negative blood type. Click here to understand why you got your mom's A blood type and not your dad's O (although either was possible). Phew! Lots of good questions here! We won't deal with the A and O parts of your blood type.
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