# Help required.

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In a post I made this statement and have forgotten where I read on it and would appreciate any help in proving my point. The poster I was adressing does not believe that if one's only purpose is to save a genetic line, that it is more advantagious to save a sibbling than a son.

Greatest I am wrote:

Your parents are a and b. You and your siblings are 1/2a and 1/2b Your children are ½ of 1/2a and 1/2b + ½ of your wife 1/2c + 1/2d ---- c and d coming from her parents. Note that your closest match is your siblings and not your children.

"Please provide evidence because I believe you are completely making that up."

To date I have been unable to link to anything that proves my point. If you can help, I would be thankful.

Regards

DL

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I think you are correct in the case of identical twins because they share 100% of the DNA but otherwise the proportion is the same between parents and children, and between siblings which is 50%.

http://www.joshuakennon.com/how-much-dna-do-you-share-with-your-blood-relatives/

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Hmm, is help ever required? That's an interesting ethical question. How do you answer it?

Greatest I am wrote:

Your parents are a and b. You and your siblings are 1/2a and 1/2b Your children are ½ of 1/2a and 1/2b + ½ of your wife 1/2c + 1/2d ---- c and d coming from her parents. Note that your closest match is your siblings and not your children.

This equation only determines how it would be best to preserve your parents' variations, but you only have half of each parent's variations, unless they share some variations. Note that I am defining "variation" in the context of the entire population. But they are no more likely to share variations than you and your wife are. You would probably be right if the parents were very similar genetically, because that would result in highly similar offspring.

Also, if a DNA test isn't available, they could choose among siblings on the basis of sex. Similarly sexed siblings will share at least one of their chromosomes, assuming they have the same father. The daughters got daddy's X, and the sons got daddy's Y.

On the other hand, a sibling that doesn't have the same father will only have 1/4 of your DNA.

Edited by Mondays Assignment: Die
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Hmm, is help ever required? That's an interesting ethical question. How do you answer it?

This equation only determines how it would be best to preserve your parents' variations, but you only have half of each parent's variations, unless they share some variations. Note that I am defining "variation" in the context of the entire population. But they are no more likely to share variations than you and your wife are. You would probably be right if the parents were very similar genetically, because that would result in highly similar offspring.

Also, if a DNA test isn't available, they could choose among siblings on the basis of sex. Similarly sexed siblings will share at least one of their chromosomes, assuming they have the same father. The daughters got daddy's X, and the sons got daddy's Y.

On the other hand, a sibling that doesn't have the same father will only have 1/4 of your DNA.

Thank you both. I think I have confirmed my point and will pass this on to my friend and see if he agrees.

If you are interested in this issue, you can find it here-------

http://www.rationalresponders.com/forum/33322?page=1

If he has questions I will let him ask those here who likely know more of this issue than I do. For me, it was more of a math question.

Regards

DL

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This equation only determines how it would be best to preserve your parents' variations, but you only have half of each parent's variations, unless they share some variations. Note that I am defining "variation" in the context of the entire population. But they are no more likely to share variations than you and your wife are. You would probably be right if the parents were very similar genetically, because that would result in highly similar offspring.

I find this a little confused and I am not entirely sure what you mean by this.

The simplest way to consider this is by the proportion of genes which are shared.

Your parents are a and b. You and your siblings are 1/2a and 1/2b Your children are ½ of 1/2a and 1/2b + ½ of your wife 1/2c + 1/2d ---- c and d coming from her parents.

This is not entirely correct because some keywords are missing. Your parents are a and b. You and your sibling are 1/2a and 1/2b, however you and your sibling share an average of 50% of your genes. Your children will share 50% of your genes (your equation is correct so I won't re-write it).

Now this is not correct for all instances. The correct answer is, it depends. The % of genes shared by siblings can vary since the average % of genes shared by siblings is 50%, it can be lower than 50 or higher than 50. The reason that this is so is because of meiosis. The father and mother of the siblings have two copies of each autosome, and only one copy is received from each parent. So the siblings can inherit different copies of each autosome from each parent meaning they are unlikely to share many genes (there are assumptions being made here but you can see how it is possible).

The % of genes shared by a father and son is 50% all the time. So the answer is dependent on the % of genes shared by the siblings, if it is lower than 50 then the father and offspring share more genes and are more closely related, vice versa.

This is a simple answer (ignoring many things which make it more complicated).

Edit: That diagram makes the assumption that the average shared genes is always 50% without mentioning it, so it is a little misleading with regards to correcting that statement you made. Also the diagram makes the assumption that the gamete which fertilised the eggs has an equal amount of parental and maternal DNA (this is in meiosis, so read up about that to learn where the averages come from if you still are not sure) (not true, again it is an average of 50% from each), this basically means that you can share more genes with your great great grandmother than you do with your great great grandfather.

Edited by jp255
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I agree with jp255, during chormosomal recombination the ratio between the two is not always 50% , but around 50%. For example this means that you can have 23% of your grandpas and 27% of your grandmas genese on your mothers side, due to the recombination of the chromosome in your mother. You still will always recieve 50% of the chromosomes from your mother (23%+27%=50% ehhhh math)

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Siblings are 0-100% "you" but tend to be very close to the average of 50%. Offspring are 50% of "you".

Essentially, in terms of who to prioritize saving, offspring are the new car and siblings are what's behind door number 2.

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