Poll: Read OP.
Poll Options
View poll results: Read OP.
Cousin
30 29%
Half-sister
57 56%
Not enough information to say.
15 15%
Voters: 102.
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#1
My sister asked me an interesting question, and I wanted to see what you guys think.

Okay, I have 1 half sister, and a cousin.

My half sister is the daughter of my dad, and his ex-wife, another completely random woman.

Now, my cousin is this (kind of confusing): Before my mom and dad started dating, my dad's older brother and my mom's older sister were married (which is how they first met). They ended up divorcing because he cheated a lot and drank/did drugs too much, but they had a kid. Which is my cousin.

So she is the daughter of both my uncle on my dad's side and aunt on my mom's side (both the aunt and uncle I'm related to "by blood"). No incest or anything is here, yada yada.

Who is my DNA most similar to; Half- sister, or cousin?

I'm thinking it's my cousin, but I'm not sure.
#2
Half-sister

Reading the cousin bit was a little confusing but I do remember my bio professor saying that half-sibling DNA is more similar to yours than a 1st cousin's DNA.
Last edited by Masamune at May 6, 2011,
#5
This thread would be easier to understand if it was represented on a...
A. Spread sheet
B. Power point
C. Venn Diagram
D. Flow Chart.

The answer is D
#6
your half sister, because both you and her descend directly from your dad.
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#7
Quote by ABRfan
This thread would be easier to understand if it was represented on a...
A. Spread sheet
B. Power point
C. Venn Diagram
D. Flow Chart.

The answer is D



Or maybe by learning some basic genealogy...
#9
Quote by Masamune
Half-sister

Reading the cousin bit was a little confusing but I do remember my bio professor saying that half-sibling DNA is more similar to yours than a 1st cousin's DNA.


Yeah but that's assuming either the aunt/uncle is from another bloodline, here the aunt and the uncle are both blood related, being siblings of both of his parents so I'd say that your cousin is in ths case.
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#11
Your half-sister will have more similar DNA to you as you both received DNA from your dad.

You receive 23 chromosomes from each parent to form the complete 46. These are random. There are only 46 so it is likely that you and your half sister do have some of the same chromosomes, but not all. You could have each received an entirely different 23. However, you both share DNA with your dad.

Your mother and her sister will probably have some of the same chromosomes as will your dad and his brother but by the time you get to your cousin the chances of you sharing any chromosomes decreases. Your cousin may have NO chromosomes that your dad has.

EDIT: strike that. I read the next post. Now I have no clue lol. Threadstarter... why you make my brain work?
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Last edited by p-nutz at May 6, 2011,
#12
Presuming your dads older brother descended from the same parents as your dad, and your mums older sister descended from the same parents as your mum, then you and your cousin have the same grandparents, where as your half-sister only shares 2 of your 4 grandparents, ergo your cousin wins.
#14
^^I would say full sibling 1
half sibling 1/2
cousin 1/8
double cousin 1/4?

So I guess half sibling
#15
Quote by Neiliorox
^^I would say full sibling 1
half sibling 1/2
cousin 1/8
double cousin 1/4?

So I guess half sibling

Full sibling is 1/2. You would only share 100% of your DNA with an identical twin.
#16
Quote by technicolour
full siblings 1/2
half siblings 1/4
cousin 1/8
iirc


This holds true except that his cousin would be recieving double the amount of similiar DNA since its from two related sources, so it would make the two appear to be equal. However, I believe by p-nutz logic that you and your half-sister and both recieving DNA directly from a parent, that the likehood of similiar DNA is more despite that equalivent fraction.

Don't count me on it though, we need some sort of expert up in this bitch
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#17
Cousins are 1/4 of your DNA. Siblings are 100% you. Half siblings are 50% you.
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#18
half sibling because neither of your parents birthed your cousin.
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#19
Mind ****...
Ziphoblat makes sense. But I have no idea.

Also, flow chart would help
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#20
Quote by poopsmith666
your half sister, because both you and her descend directly from your dad.


This.
#22
1/2 of your genetic makeup comes from each of your parents. 1/2 of theirs comes from their parents. 1/4 of your genetic makeup comes from each of your grandparents.

Your half-sister shares your father. 1/2 of your genetic makeup is shared.

Your cousin comes from your father's brother and your mother's sister. Your uncle shares parents with your father (obviously), as does your aunt with your mother.

Your cousin shares all 4 grandparents with you. This is a greater genetic similarity than sharing 1 parent, which is the equivalent of 2 grandparents.

And yeah, I know I'm simplifying it, but the gist remains the same.
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#23
I think it would be your cousin because you're both descended from the same grandparents.
#24
Quote by MAC2322
1/2 of your genetic makeup comes from each of your parents. 1/2 of theirs comes from their parents. 1/4 of your genetic makeup comes from each of your grandparents.

Your half-sister shares your father. 1/2 of your genetic makeup is shared.

Your cousin comes from your father's brother and your mother's sister. Your uncle shares parents with your father (obviously), as does your aunt with your mother.

Your cousin shares all 4 grandparents with you. This is a greater genetic similarity than sharing 1 parent, which is the equivalent of 2 grandparents.

And yeah, I know I'm simplifying it, but the gist remains the same.
This is what I think. Surprised Half-sister is taking such a lead, though.
#25
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#26
you're just trying to figure out which one to go for, in order for wincest
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#27
I say cousin, but I only read half of the OP.
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#28
Your cousin. I didn't think about it too hard but I have a cousin whose parents are my mom's sister and my dad's brother and she looks exactly like me except she's taller.
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#30
In your weird case, your cousin has more similar DNA to you.

This really shouldn't be a poll situation though. Don't ask the masses, ask the geneticists
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#32
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only from texas...

I don't see how that is even relevant.


The half sister would be. The cousin is kind of like a double first cousin since their parents are siblings of both parents but since the common denominator between those siblings is their parents DNA then it wouldn't really apply very much, it's just an odd situation. The sister has half of your dad's DNA. The cousin has half of your dad's brother and half of your mom's sister and they have different DNA than your parents.

Fun fact: My grandma and her sister married two male cousins so my great aunt and uncle are also my cousins. It's always a little awkward trying to explain how I have double relations without inbreeding.


EDIT: Maybe it's an equal relation. I think since sex cells are made to be unique, a direct descendent would give more relation than four common grandparents as opposed to two.
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Last edited by BladeSlinger at May 7, 2011,
#33
Quote by Jostry
Cousins are 1/4 of your DNA. Siblings are 100% you. Half siblings are 50% you.


ert. Only identical twins are 100%

You clearly didn't read the first post anyway... so it doesn't matter

I've been thinking about it a bit more and now I'm not so sure about what I said.. I still can't be bothered getting a pen and paper and figuring it out though. Now my brain is telling me that you probably share the same amount of DNA with both the half sister and the cousin. Really I think it kinda depends on the specific cousins genetic make up. We don't know what genes your parents share with their siblings, so we don't really know what would have been passed on to you and your cousin blah blah etc blah..

EDIT :
Quote by BladeSlinger


EDIT: Maybe it's an equal relation. I think since sex cells are made to be unique, a direct descendent would give more relation than four common grandparents as opposed to two.


It was your post that made me rethink my original post We seem to both have come to the same conclusion now
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Last edited by Domino at May 7, 2011,
#34
Quote by Domino
ert. Only identical twins are 100%

You clearly didn't read the first post anyway... so it doesn't matter

I've been thinking about it a bit more and now I'm not so sure about what I said.. I still can't be bothered getting a pen and paper and figuring it out though. Now my brain is telling me that you probably share the same amount of DNA with both the half sister and the cousin. Really I think it kinda depends on the specific cousins genetic make up. We don't know what genes your parents share with their siblings, so we don't really know what would have been passed on to you and your cousin blah blah etc blah..

EDIT :


It was your post that made me rethink my original post We seem to both have come to the same conclusion now


Ignoring genetic mutations, the cousin would be more genetically similar. Factoring in genetic mutations, that still holds true, but is less obvious.
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#35
Quote by MAC2322
Ignoring genetic mutations, the cousin would be more genetically similar. Factoring in genetic mutations, that still holds true, but is less obvious.


Not necessarily. It really depends on which genes both TS and the cousin inherited from their mothers and fathers side.
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#36
Quote by Domino
Not necessarily. It really depends on which genes both TS and the cousin inherited from their mothers and fathers side.


The deviation that comes from that is too small to account for the fact that TS's cousin shares all 4 of his grandparents with him while his half-sibling only shares 2.
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#37
Quote by MAC2322
The deviation that comes from that is too small to account for the fact that TS's cousin shares all 4 of his grandparents with him while his half-sibling only shares 2.


Its not too small at all. TS's parents and cousins parents (that are siblings) can be seen as 50/50. From that TS and cousin get 25/25 (with that extra 50 floating around for each parent that isn't identical to that in the cousins parent). Their genetic similarity _could_ easily be higher than his and his half sister. To say that it is is wrong though because we don't know their genetic make up
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#38
Quote by Domino
Its not too small at all. TS's parents and cousins parents (that are siblings) can be seen as 50/50. From that TS and cousin get 25/25 (with that extra 50 floating around for each parent that isn't identical to that in the cousins parent). Their genetic similarity _could_ easily be higher than his and his half sister. To say that it is is wrong though because we don't know their genetic make up


TS's mother comes from her parents. So does her sister. The difference between the two is not hugely significant, since they're siblings. The same can be said of TS's father and TS's uncle.

It follows, then, that the genetic difference between the children of these is about the same as the double the difference between two siblings. This is less difference than that of a half-sibling, which shares one parent while the other is completely different. That means even if there were no mutations, the half-sibling could have a maximum of 50% genetic similarity, while the cousin could have upwards of 90%.
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#40
Quote by MAC2322
TS's mother comes from her parents. So does her sister. The difference between the two is not hugely significant, since they're siblings. The same can be said of TS's father and TS's uncle.

It follows, then, that the genetic difference between the children of these is about the same as the double the difference between two siblings. This is less difference than that of a half-sibling, which shares one parent while the other is completely different. That means even if there were no mutations, the half-sibling could have a maximum of 50% genetic similarity, while the cousin could have upwards of 90%.


The cousin can have upwards of 50, not 90. You're assuming that the same 50% of genes where inherited by the mother and her sibling and the father and his sibling which is completely unlikely, unless the parents are identical twins. That's kinda the way maths teaches you to think which is why I initially came to that conclusion myself.

EDIT: I don't know why I said the cousin can have upwards of 50, I dont know what the cousin can have upwards of, I haven't sat down with a pen and paper and tried to work it out
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Last edited by Domino at May 7, 2011,
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