DNA of first cousins?

Adele from what I understand, each child does not necessarily get 25% of their Autosomal DNA from each grandparent. They get 50% from their paternal grandparents and 50% from their maternal grandparents but it will not be an even breakdown between grandmother and grandfather on both sides of the family. How you inherited this bias will not be how your siblings inherited it unless you have an identical twin. So simple fractions determining really won't be accurate. I had a question about Autosomal DNA which I asked on the Biology Board since I had seen a website that said you don't get Autosomal 50% from each parent. Here is the reply I received:

"Actually, you do inherit your autosomal DNA 50-50 from each parent. That site is wrong.

"Your mother's egg contributes one set of 22 autosomes and one sex chromosome (an X). Your father's sperm contributes the other set of 22 autosomes, and another sex chromosome (either an X or a Y).

"Where the 50-50 part breaks down is when you pass on your DNA to your children. Each of your children will get half their DNA from you, but they won't necessarily get an equal mix of what you inherited from your parents. They could inherit a more from your mother, through you, and less from your father, or vice versa.

"Another way to look at it: you inherited 50% of your autosomal DNA from each parent, but you didn't necessarily inherit exactly 25% from each grandparent. Your maternal grandparents contributed exactly 50% in total, but it could be biased in favor of either your maternal grandmother or your maternal grandfather. Same goes for your paternal grandparents.

"When you take one of those DNA tests, which markers they find depend on which ones you inherited through your mother and father, and that will be different between you and your siblings (assuming no identical twins). If one of your grandparents is Dutch, and another is Polish, you might happen to inherit more markers that the test considers NW Eur., and your sister might happen to inherit more that are considered E Eur. In most cases, that will just be a random chance. Also, just because you have more markers that the test considers NW Eur, doesn't necessarily mean you really are "more" NW Eur. in any real sense.

"As to your last question, I'm pretty sure that most of the variation in what DNA you inherit vs. what your siblings inherit is quite random. I don't think an ancestor from 1700 could somehow dominate the DNA markers in his/her descendents overall. Certain single markers could do that, if they conferred some advantage, but most will be essentially random.

Source(s):

PhD in molecular biology"

So it definitely appears DNA wise you can be more closely related to one sibling over the other and one first cousin over the other. Autosomal is really why most of your DNA is. It is what determines your appearance, pigmentation, height etc. Forty-four of your 46 chromosomes are made up of Autosomal DNA. However, I found another website that says only 2% of your DNA makes up your chomosomes the other 98% determine how the DNA interacts.

http://www.pa.msu.edu/~sciencet/ask_st/060293.html

Edit: Dr. J provides an excellent link. I am bookmarking it.

DNA is not "measured" in the same manner as generational relationships. It is not something that is divided neatly into a mathematical formula. You might want to check some of the sites that explain DNA and what the results actually mean.

For a very good look at this topic, see the essay by a geneticist with diagrams.

http://www.thetech.org/genetics/ask.php?id=284