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What blood types make R-?

(18 Posts)
Davros Wed 04-May-16 17:33:13

I need to find out which blood types parents of a child with Rhesus Negative would have? This is to try to narrow down who may be the biological parent discreetly

MrsPigling Wed 04-May-16 17:36:00

you can't narrow down blood types for Rh- as it's a dominant gene so someone who is Rh+ may carry one gene for -ve and one for +ve.

Davros Wed 04-May-16 17:45:47

Thanks for the info and link. I am finding it all quite impenetrable but here is some extra info:
Child is Orh negative
One parent is Orh positive
Is it possible to narrow down what blood type(s) the other parent would have to be?

RockCrushesLizard Wed 04-May-16 17:49:03

The other parent needs to be O-ve (though there are some very unusual blood groups/combinations that can give current results, so there is a tiny chance otherwise)

Gizlotsmum Wed 04-May-16 17:49:24

They would need to be o as that is recessive but could be rh + or - as explained above. Why so cloak and dagger

Davros Wed 04-May-16 18:01:38

One parent believes they are the biological parent but may not be. So I am looking for ways to find out without giving the game away. I also need to find out if a DNA test can be done without the knowledge of one parent. I doubt it.
Thanks for your help

MrsPigling Wed 04-May-16 18:02:32

The other parent could be any type I think. Look in link at brightly colour table in genetics section

the pale red, pale blue and pale purple combinations could be O blood despite one parent being A or B (but not AB)

jellycat1 Wed 04-May-16 18:03:42

I'm O neg and my older son is too. My husband is A.

Lunar1 Wed 04-May-16 18:04:04

I'm pretty sure you need to get consent for DNA.

Gizlotsmum Wed 04-May-16 18:06:03

Actually yes o is recessive so anything other than ab could be the parent..

InTheSandPit Wed 04-May-16 18:12:36

I don't think the other parent can be AB, but a parent with A,B or O blood could make an O child.
RH status could be either.

Davros Wed 04-May-16 18:22:38

Thanks. I expect permission is required for a DNA test but that would mean huge upset and the "unaware" parent could turn out to be the biological parent anyway. Tricky

HyacinthBouquetNo1 Wed 04-May-16 18:45:31

I am curios about this, tried to read up on it but its quite mindboggling!

I am A positive, one of my children is A positive but the other is A negative. We dont know what my husband is and have wondered if he had to be negative to have the A neg child? But not sure

Somerville Wed 04-May-16 18:58:54

Hyacinth, we each have 2 copies of our blood type. (1 from each parent)
With the Rhesus factor, if you have it from either parent, you are rh+.
Since you know that one of your children is negative, and you are positive, you must have Rh+/Rh-

You have passed your Rh- to your negative child, and they must have also got a Rh- from your DH.
You have passed your Rh+ to your other child, and they either have Rh- or Rh+ from your DH.
Your DH could be either Rh+/Rh- (and therefore Rhesus positive) or Rh-/Rh- (and therefore Rhesus negative.)

Does that make sense now or have I just confused you further?!

Somerville Wed 04-May-16 19:00:00

Davros, are you one of the parents? confused

HyacinthBouquetNo1 Wed 04-May-16 19:04:14

Somerville, thank you, thats a very clear explanation, i understand it a bit better now!

Somerville Wed 04-May-16 19:11:12

Oh good. smile

I've explained it in RL with sweets and pieces of paper saying this-is-not-a-sweet and was just working out if I could do it with biscuit !

If 1 parent gives you a biscuit and the other gives you something saying not-a-biscuit then you have a biscuit.
You can give your child the biscuit or the not-a-biscuit.

Davros Wed 04-May-16 19:44:18

No, I am not I e if the parents (thank god!) but it is someone very close to me who is distraught and I want to help emotionally and practically

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