Basic mendelian genetics, relatedness to brother andn terms of percent genes shared pic appreciated?

Question

Me and my friend were having an argument about genetic relatedness between brother and sister, aunt and cousin. He thinks that brother and sister are 100% related in terms of genes while I try to tell him that we receive 50% random genes from each parent giving each sibling only a 50% relatedness.

I also remember some interesting facts about genetic relatedness between ant sisters being higher than the relatedness to their mother, 66% for sisters, 50% or less (not sure for mother)

Can someone find me some concrete evidence from a reputable source backing up all these facts which I am 100% sure are true. Neither of us will back up on this argument and google nor my other references are of any help.

The Wikipedia article on mendelian genetics doesn't suffice, I need proof for humans, is it true all our genes are perfect examples of mendel's laws?

Answer 1

How does 50% random genes from each parent equate to 50 percent relatedness? It's the same genetic information, just arranged differently, isn't it? That figure seems strange, as does this question. It's all random if you ask me.

Answer 2

This will allow you to prove that brother and sister are not 100% related:  http://hcs.osu.edu/hcs300/genetic.htm

It is due to the random selection of genes provided in the gametes (sperm and egg), produced by a combinatiion of mitosis and meiosis that gives us genetic different to those of our brothers and sisters.

The production of sperm is explained in this diagram, it shows how each sperm carries a different combination of genes so it is not possible for siblings to be 100% alike... or we would all be identical... http://users.rcn.com/jkimball.ma.ultrane...

So we have 50% of each of our parents genes (but not necesserily 50% the same visually as it depends on the dominant and recessive genes and the arrangement of genes).

Mendel used peas to demonstrate dominant and recessive alleles, which is genetic inheritance.

I am not quite sure what you are trying to get at in the second paragraph...?

Answer 3

Wow! That's one of the best questions I think I've read on Yahoo Answers!

Unfortunately I'm not good enough with Mathematics to help you, but that's what I suggest that you consult along with information from Genetics on this "random" selection of chromosomes.

It does "make sense" though that siblings would be closer to each other than to a single parent (as long as the parents aren't related :)

We all have a total of 46 chromosomes with each diploid cells having two sets of 23 chromosomes, (each set coming from one parent), ergo your "50%."

It doesn't help matters that these are all random either.

Their still "related" either way.

Great question!