cousin more like sister

del88

Well now I've got your attention..
My mothers brother married my fathers sister.....so I have double cousins ,just wondering if there was anyone out interested in studying the genes from me and my cousin to see how close we would be genetically...

Kevster

Your question is rather confusing. Are you first of all implying that you're married to one of these cousins? - i.e. the daughter of your married uncle and aunt? There isn't necessarily much genetic similarity between you both. If you married your sister, then you obviously share half of your DNA with her. However, if you married a cousin as you have implied, then it becomes much further diluted:

Your mother shares half of her DNA with her brother/sister (your uncle/aunt). He/she then passes half of his/her own DNA to his daughter (your wife). So, your wife would share one-quarter of the same DNA as you. If you then add the other quarter (from the other side of the family), then it does indeed add up to half-genetic similarity...

...weird.

Kevin

del88

Kevster wrote: »

Your question is rather confusing. Are you first of all implying that you're married to one of these cousins? - i.e. the daughter of your married uncle and aunt? There isn't necessarily much genetic similarity between you both. If you married your sister, then you obviously share half of your DNA with her. However, if you married a cousin as you have implied, then it becomes much further diluted:

Your mother shares half of her DNA with her brother/sister (your uncle/aunt). He/she then passes half of his/her own DNA to his daughter (your wife). So, your wife would share one-quarter of the same DNA as you. If you then add the other quarter (from the other side of the family), then it does indeed add up to half-genetic similarity...

...weird.

Kevin

Sorry ,your right, title was confusing.... i was just wondering if anyone was interested in examing a sample of my dna and my cousins to see how sinilar it was.....

Kevster

I dont think that you'll get any response that you are looking for, to be honest. You can send your and your wife's DNA to a sequencing laboratory, however, and they can sequence and compare the two. I don't think it's too expensive to do this type of thing these days, as sequencers have improved vastly over the past decade even.

Kevin

JackieChan

I think people need to read what the OP is saying clearly.
There is no mention of his wife or even that he is married!

My partner is an indentical twin, and the children from each side are pleased that they are genetically as much half-sisters as cousins!

A lot of similarities between the children too, naturally enough!!

Kevster

JackieChan wrote: »

I think people need to read what the OP is saying clearly.
There is no mention of his wife or even that he is married!

My partner is an indentical twin, and the children from each side are pleased that they are genetically as much half-sisters as cousins!

A lot of similarities between the children too, naturally enough!!

True, although I had asked indirectly for him to clear up what he was implying. I don't know why I assumed he was married to her... ...but I did ask. I never thought about how strange it'd be to be in your situation though, JackieChan - It's weird!

Kevin

Capt'n Midnight

50:50 your cousin is the same sex as you are.


IIRC in the states it's about $70 per sample, depending on which markers you are looking for

you would probably need DNA from the parents too so figure 6 samples , or even the grandparents


Unless you have some special genetic trait then I can't see anyone being interested in what is more or less a probability study.
23 chromosome pairs
50:50 chance of which half pair inherited from each parent.
Just like everyone else on the planet.


Just reading it again to clarify your parents siblings got married.
Double cousins would have been much more common in previous times when there was less travel. But they would not be kissing cousins.

darjeeling

We share 50% of our genes by descent with our parents, 25% with their siblings and - typically -12.5% with their siblings' children (our first cousins). In your situation, though, each of your cousins' parents shares 25% of their genes with you, so your cousins will also share 25% of your genes. This means your first cousins are as related to you as are your blood aunts and uncles.

I don't know if marriage laws take account of this sort of relationship. In the UK, 2nd-degree relative marriages (e.g. marrying a niece or nephew) are illegal, but first cousin marriages are not. However, if someone were as related to their first cousin as they would be to a 2nd-degree relative, I guess a marriage would be legal nonetheless?

.

Scoobydoobydoo

This isn't that uncommon, I've come across it a few times. My mother has some double cousins also. My grandmother's brother married my grandfather's sister. I don't know what the genes say, but it's never been said that these cousins are in any way outwardly like her or her siblings.

Kevster

darjeeling wrote: »

We share 50% of our genes by descent with our parents, 25% with their siblings and - typically -12.5% with their siblings' children (our first cousins). In your situation, though, each of your cousins' parents shares 25% of their genes with you, so your cousins will also share 25% of your genes. This means your first cousins are as related to you as are your blood aunts and uncles.

I don't know if marriage laws take account of this sort of relationship. In the UK, 2nd-degree relative marriages (e.g. marrying a niece or nephew) are illegal, but first cousin marriages are not. However, if someone were as related to their first cousin as they would be to a 2nd-degree relative, I guess a marriage would be legal nonetheless?

.

Is it not 50% like I said? You have to add another 25% from both the uncle and aunt of the OP. That makes 50%... ...I think I'm right? I explained it better in my first post here.

Kevin

Tree

I think, strictly speaking here, 25 + 25 does not equal 50. it probably remains at 25% max. you'd have to find someone who's handy at stats though

Kevster

Tree wrote: »

I think, strictly speaking here, 25 + 25 does not equal 50. it probably remains at 25% max. you'd have to find someone who's handy at stats though

True, I suppose.

darjeeling

Kevster wrote: »

Is it not 50% like I said? You have to add another 25% from both the uncle and aunt of the OP. That makes 50%... ...I think I'm right? I explained it better in my first post here.

Kevin

Afraid not. Your aunt and uncle each pass on 50% of their genes to their children. If your aunt is related to you by blood and your uncle isn't, then your aunt shares 25% of your genes by descent, and your uncle 0%*. Your cousin,then, gets 50% of the 25% of genes your aunt shares with you, and 50% of your uncle's genes, none of which are shared with you. So, 50% of 25% plus 50% of 0% equals 12.5% of your first cousin's genes shared with you. This is the basis of JBS Haldane's quote: "I would lay down my life for two brothers or eight cousins."

Now, if your aunt and uncle are both your blood relatives - as per the OP - then the figure is 50% of 25% + 50% of 25% = 25%.

*In reality these percentages will be higher, as we're all in-bred, but I'm talking theoretically here.

Capt'n Midnight

darjeeling wrote: »

*In reality these percentages will be higher, as we're all in-bred, but I'm talking theoretically here.

Depending on who you believe then excluding Africans the rest of us are genetically equivalent to sixth cousins.


Re: When 'double cousins' have children how great are the genetic risks?
comparing how likely it to get two copies of a defective allele for a particular gene, ie. how likely they are to have the same genes
http://www.madsci.org/posts/archives/2002-02/1014847561.Ge.r.html


line 19 - note the different rates for inheriting sex linked genes - but it's fairly easy to tell if the cousins are of similar sex or not
http://www.nature.com/hdy/journal/v97/n5/fig_tab/6800895t5.html

Kevster

Why amen't I seeing this then... ...Why doesn't an aunt/uncle share 50% with us?

Edit - I see it now. Man, I'm turning dumb these days.

Kevster

I came across these companies in my own research. They can do SNP analysis, which is pretty much the best you'll be able to afford I'm guessing. A complete sequence of a human's DNA is still expensive.

https://www.23andme.com/
http://www.navigenics.com/
http://www.decodeme.com/

Kevin

iguana

darjeeling wrote: »

I don't know if marriage laws take account of this sort of relationship. In the UK, 2nd-degree relative marriages (e.g. marrying a niece or nephew) are illegal, but first cousin marriages are not. However, if someone were as related to their first cousin as they would be to a 2nd-degree relative, I guess a marriage would be legal nonetheless?

That's a pretty interesting side-issue especially in a situation where identical twin-sisters have married identical twin-brothers. In that scenario the offspring of each union are genetically siblings but legally cousins.

emmiou

coefficient of inbreeding The probability that two allelic genes forming a zygote are both descended from a gene found in an ancestor common to both parents. It is also used for the proportion of loci at which an individual is homozygous. The coefficient of consanguinity of an individual is the probability that two homologous genes drawn at random, one from each of the two parents, will be identical, and therefore homozygous in an offspring. The term is sometimes known as Wright's inbreeding coefficient (F), after the geneticist Sewall Wright who formulated it. F = ½ for a selfed mating; ¼ for fullsib mating; 1/8 for uncle × niece and aunt × nephew, or double first cousins (i.e. cousins by both parents); and 1/16 for first cousins.