Randomness of inheritance

Thinking about randomness of inheritance as I work my way through the autosomal DNA results for my birth family lines. I thought I might write a macro to make a fast job of this but really I have to look at each line just because that works best for me. Even if another sibling tests then I would do it exactly the same way inserting their results in their birth order. One is left to wonder does birth order matter or is randomness the normal way for passage of DNA from parent to child during fertilization. Does age play a role at all; some diseases are said to be more prevalent in an aging parent than a younger parent. Do some of these genes age in such a way that adenosine becomes more dominant and aggressive in a fertilization process than say guanine or cytosine or thymine? An intriguing thought once you get down to decision making time on particular snps. One can just leave out the snps that one is unsure about and then create a file that you can then upload to gedmatch or can you? I shall have to debate that one for a bit. Gedmatch lets you look at particular lengths of a chromosome which is fascinating in itself. I will buy the extra tools once I have something in hand to work with on this idea of mine.

As a child I always felt different from my siblings and thus far my genetic complement is very different from them although enough sameness that I know we are siblings. I was number four child in a family of seven. My grandmother used to say that I was like her mother and amazingly that could actually be true. My siblings match a Pincombe twice as much as I do (my maternal grandfather) and my match with a known cousin of my grandmother on her father's side which is third cousin looks like a 4th to a 6th cousin on Ancestry so did I also get less of Buller. That only leaves me with Gray (my maternal grandfather's mother) and Taylor (my maternal grandmother's mother). Could she indeed be right that I resembled her mother. My grandmother's mother died when my grandmother was eleven. My grandmother saw her as a woman who spent all of her married life bearing children. My grandmother was the eldest and remembered the birth of her next in line sister and my grandmother would have been almost four years of age at that time. I can remember an event when I was just four years old so I can believe her story. Ada was a blue baby and born just under eight months gestation. She was kept in a bun basket near the stove to keep her warm which was probably why my grandmother remembered it so very well. Her mother had dark hair as mine was (now tinged with grey) but she did have grey eyes and mine are more hazel than grey. She was a tall slim woman probably about my height I suspect but tallness to an 11 year old is a lot of people. What reminded her of me characterwise was my hyperactivity. I was always in motion and that was how she remembered her mother. Plus I loved to sing as did her mother.

A child receives 50% of their DNA from their father and 50% of their DNA from their mother hence making it easy to work out if you have both parents or one parent and a child the likely DNA of the third member. But when you reach back to a grandparent and the amount of DNA they pass to a grandchild that can be quite variable. It could be that 25% is passed by each grandparent but this passing is done in the parent's body so that at fertilization chunks from each of their parents are rearranged at fertilization so that one could actually get nothing from one grandparent and the entire 50% that a parent contributes could have come from the other grandparent. When you reach great grandparent that you are talking about an average of 12.5% of their DNA passing to their great grandchild. The significance of ancestors in the DNA disappears rapidly - 50% in each generation because there are eight great grandparents to contribute to one child. You could have four of the eight contributing to that child and four not which would result in no matches with those lines or you could have the average 12.5% contributed by each great grandparent or some number in between 0 and 25%.

The maximum I could have received from my grandmother's mother then could be as high as 25% if at conception my mother passed DNA to me that consisted of 25% Taylor and no Buller. However I know that I match a Buller third cousin but it could be on the Welch side as a Buller married a Welch and they were my 2x great grandparents and that might account for the 4th to 6th cousin match instead of a 3rd cousin match. Thinking about it it is entirely plausible that I acquired closer to 25% Taylor and that was why my grandmother noticed that I seemed somewhat like her mother in both looks and character. However I must have also acquired some Welch, enough to match as a 4th to 6th cousin. My mother received 50% of her DNA from her mother which would of consisted of Buller and Taylor from her grandparents but the Buller included Buller and Welch and the Taylor included Taylor and possibly Roberts. That is what is so random about all of this we can get chunks that have passed down virtually intact from several generations back and they are our 4th, 5th and 6th cousin matches.