(EDITED - a lot of what I am saying is implicit and simplified. I'm not looking to recreate the numerous textbooks and scientific papers on how DNA works).
As far as I can understand it, an organisms basic building blocks (proteins) are made up of DNA, Genes, and Chromosomes. The most basic form of this is DNA, made up of molecules in double helix strands. DNA carries all the instructions for the body in a simple 'database' or 'blueprint' form. Genes are chunks, or sequences, of the DNA telling the body 'what to do'(1) by reading the 'DNA database' in a myriad of unique coding sequences. Genes naturally(2) switch on and off throughout an organisms lifespan allowing amongst other things for an organism to grow from young to old. DNA is essentially(3) stored in Chromosomes.
External and environmental factors can influence the expression of genes, and the information stored in the DNA (4) - the study of which is Epigenetics. These Epigenetic factors can change over time, switching genes on and off. (5)
Does the body store a history of these expressions? Do the chromosomes (or some other part) of an older organism store a 'user-history' of which genes where previously activated when the organism was younger? eg, can you tell which genes where active when a person was 12, from the cells of an 80 year old?
Apologies, I do not have a background in Biology. (6)
(1) what to do, how to do it, when to do it. not necessarily all life supporting instructions but also the minute-to-minute, day-to-day processes etc.
(2) naturally. there is no black and white in nature, only shades of grey.
(3) essentially. not exactly and not in all cases but mostly.
(4) As in, factors influence the expression of genes (which in turn are made up of DNA information). I am not suggesting that external factors can influence the 'DNA database' itself but rather just how they are 'read', sequenced and expressed as genes.
(5) again, naturally. no sharp on/offs but variations of concentrations.
(6) I may not have used the correct terminology.