Rhesus Negative Factor

[diplodicus]

a genetic link amongst people who are rhesus negative and if it could help with DNA testing and tracing ancestors.

Well, your Rhesus factor is determined by your genes but it is unlikely to help you to trace ancestors. It can only eliminate certain parent/child uncertainties and only if you know which Rhesus factor each carries. This would enable you to say when they are not related; two Rh- parents cannot have a Rh+ child.

[LizzieW]

two Rh- parents cannot have a Rh+ child.

I guess it's possible if the Rh parents are Rh-/Rh+.  In my case my parents were both Rh+ but I turned out to be Rh- and presumably Rh-/Rh- as all my children are Rh-, yet my husband is Rh+ (so probably Rh+/Rh-.  When my parents went to become blood donors they were told their blood group meant they were positive to give but negative to receive - and it's interesting that the two of them should meet each other, especially as their near ancestors came from totally different parts of the UK!  When I was doing my midwifery training I asked the haematologist lecturer to explain to me how I could be the child of 2 Rh+ parents and it is (and obviously was) possible.  People could say I'm not my father's daughter but as I look exactly like him and his sisters, I think I probably am 

[pharmaT]

two Rh- parents cannot have a Rh+ child.

I guess it's possible if the Rh parents are Rh-/Rh+.  In my case my parents were both Rh+ but I turned out to be Rh- and presumably Rh-/Rh- as all my children are Rh-, yet my husband is Rh+ (so probably Rh+/Rh-.  When my parents went to become blood donors they were told their blood group meant they were positive to give but negative to receive - and it's interesting that the two of them should meet each other, especially as their near ancestors came from totally different parts of the UK!  When I was doing my midwifery training I asked the haematologist lecturer to explain to me how I could be the child of 2 Rh+ parents and it is (and obviously was) possible.  People could say I'm not my father's daughter but as I look exactly like him and his sisters, I think I probably am 

Two rhesus negative parents cannot have a rhesus positive child as for your phenotype to be rhesus negative your genotype has to be Rh-/Rh- as the Rh negative gene is recessive to the Rh+ gene.  A Rhesus positive parent however could have a rhesus negative child if  their genotype was Rh+/Rh- providing they had a child with someone who was either Rhesus positive with a RH+/Rh- genotype as well or someone who was Rh- (Rh-/Rh-)

[LizzieW]

Pharma - OK, I understand, so if someone has a phenotype Rh+/Rh- they are automatically Rh+ but can have Rh- neg children with someone who also has phenotype Rh+/Rh-, which is what happened in my family.  I guess as I am Rh-, so presumably with a phenotype of Rh-/Rh- and as all our children are also Rh-, my husband's phenotype must be Rh+/Rh-.  What I don't understand is why my parents were given special donor cards and were told their blood had to be treated as positive when given to someone, but negative if they needed blood.  No-one has ever told my husband that, as far as he is concerned his blood group is Rh+.  He used to be a blood donor and just had the usual coloured card for RhB+.  I used to know which coloured card meant which blood group, but I've forgotten now.  All I know is my parents both had brown cards.

[Pamela21]

I have posted this on message 49, hopefully it will answer all your questions.

[LizzieW]

Thank you Pamela21, it answers some questions.

[Gan Yam]

When my parents went to become blood donors they were told their blood group meant they were positive to give but negative to receive

Does this not mean that only positive blood groups can receive their blood as they were rh pos, but they could receive negative blood as well as positive. Depending on the blood group I’ve always understood that blood group O is the universal giver but can only receive O blood, and within that every blood group can accept O rh neg but only any positive blood types can receive O rh pos!

[3sillydogs]

Negative can only receive negative blood, but can donate to positive, group O Rh Neg is a universal donor and can be given to all, but can only receive O Rh Neg blood, as I was given to understand.  Mum was ORhNeg and was a regular donor.

[LizzieW]

The point is when my parents gave blood it was considered Rh positive so could only be given to someone with Rh positive blood.  However, if they ever needed blood themselves they would have to be given Rh negative blood.  As far as I can see this must be to do with antigens, not the well known D antigen, but some other antigen.