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(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)

EDIT NOTES

(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.

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  • $\begingroup$ Please avoid editing your post so drastically after an answer has been posted. Also, you do not have to hide your misunderstanding via loads of tiny inaccurate notes that only acknowledge that you realize you might be inaccurate. What you do not understand is of interest as it is what help people to understand what you are after and what is unclear to you. Finally, all these tiny notes look very messy and I would recommend keeping the old version. $\endgroup$
    – Remi.b
    Oct 11, 2016 at 20:16
  • $\begingroup$ @Remi.b I agree major changes may affect previous answers - I wanted to clarify the poor phrasing so future answers could focus on the question more. That's why I purposely left most of the original content intact (I pretty much only expanded the sentence about the DNA building blocks into 3 or4 sentences). I tried to leave my edits to the messy notes :) so that viewers wouldn't have to go view the previous version of the question. Unfortunately I couldn't figure out how to get subscripts for the edit notes to make it less messy. do you think listing the notes all at the end would be better? $\endgroup$
    – EveryBitHelps
    Oct 11, 2016 at 21:12

2 Answers 2

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Main question

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?

Cells can sometimes have a "memory" of the gene expression state which allows the cell to perpetuate its gene expression programme. This is facilitated by epigenetic mechanisms. Cells can also maintain a short term memory via feedbacks and switches (Casadesús and D'Ari, 2002). Immune cells store the memory of previous exposures to a certain pathogen (in this case each clonal population stores one piece of history which is unlike one cell storing the entire history). However, I don't think there is an explicit "user history" kind of mechanism. Most responses are dynamic (and memoryless); there are only a very few situations (such as immune response) that really need a history log. Usually the cellular memory is just one level deep. Storing deeper than that would cost the cell a lot.

Other corrections not directly related to the question

As far as I can understand it, an organisms basic building blocks (proteins) are made up of DNA, Genes, and Chromosomes.

This statement is extreme oversimplification. As a matter of fact, water is the most abundant molecule in the bodies of most (if not all) organisms. RNAs and proteins are essential molecules required for cellular functions. Lipids are also important as they constitute the cell membrane. Moreover, proteins are not made up of "DNA, genes and chromosomes". Your subsequent explanation of how the genes work is correct but this statement is quite wrong.

The most basic form of this is DNA, made up of molecules in double helix strands.

Misleading again. It is not correct to call DNA as "most basic form". In what way? This statement is also opinion-based.

DNA is essentially(3) stored in Chromosomes.

Chromosome is an assembly consisting of the DNA and some proteins. In a way, DNA is contained in the chromosomes. As also pointed out by Remi, your statement can have misleading interpretations.

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.

This process is simply called "gene regulation" or "regulation of gene expression". Epigenetic mechanisms (such as DNA methylation and histone modifications) are one of the mechanisms of gene regulation but they are not the only one. You can simply google "gene regulation" and you'll get plenty of resources on this topic.

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  • $\begingroup$ Thanks for the answer. Using my popular science biology background. Could the junk dna (whose purpose is not fully understood) potentially store some sort of extra information? $\endgroup$
    – EveryBitHelps
    Oct 12, 2016 at 9:34
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    $\begingroup$ @EveryBitHelps It potentially can (and would no more be junk) but storing such an extensive amount of information would require a lot of "space". $\endgroup$
    – WYSIWYG
    Oct 12, 2016 at 9:56
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First Paragraph - let's debunk what was poorly phrased

Many sentences you wrote are quite misleading. You should have a look at an introduction to molecular genetic to have a better understanding such as what you can find on Khan Academy. In short:

the double helix DNA strands are the building blocks of an organism

This sentence is very opinion based. as a matter of proof, one could for example replace the term double helix DNA by "cells" (or other terms) and many would still be satisfied with the sentence.

Genes are chunks of DNA telling the body what to do.

A gene is a part of DNA which contains regions coding for proteins. There are many sequences which are not coding for any proteins that are essential for the individual survival (such as regulatory sequences or sequence coding for rRNA for examples).

Genes naturally switch on and off.

The regulation of gene expression is actually much more continuous than just on/off. Also, regulation of protein concentration can occur at different levels and not only by regulating gene expression.

DNA is essentially stored in Chromosomes.

This sounds like chromosomes are boxes in which one can find DNA. In reality, DNA is a type of molecule which can be found under different forms. In humans (and other eukaryotes) most of the DNA (but not all) is present in the form of chromosomes.

Second Paragraph - What is epigenetics?

External and environmental factors can influence the expression of genes,

This is correct

and the information stored in the DNA

This is wrong. Environmental factors do not affect the sequence of base pairs of the DNA. It only regulate its expression. Such regulation of expression can last for a long time and even be transmitted to the offspring. The term epigenetics is loosely defined. In short epigenetics refers to the set of mechanisms that affect gene expression at short and long term. The classic mechanism of interet in epigenetics in the methylation of histone tails (quickly speaking, histones are proteic structures around which DNA is wrapped).

Your question

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?

As explained above, some of the molecular mechanisms yielding to changes in gene expression can have long term consequences on gene expression (which can even be inherited). But there is not data bank (or other centralized or not source of information) that specifically record the expression of each gene at any one time in the history of the cell life.

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  • $\begingroup$ Thanks for the answer in the last paragraph & half. I was trying not to get bogged down in the details of the basics (whole textbooks are devoted to) so that I could get to the question. I also appreciate I may not have used the correct terminology and a lot of what I was meaning was implied. But how can the first line you quoted about the DNA helix be referred to as 'cells'. eg "the cells are the basic building blocks of an organism"...no problem in itself. but now a follow up sentence "an organisms cells are found in cells"?? I'll fix the sentence idea to be clearer but not to cells. $\endgroup$
    – EveryBitHelps
    Oct 11, 2016 at 19:53
  • $\begingroup$ I was only referring to the part of the sentence I quoted. My point was that calling "DNA strands" the building blocks of an organism makes little sense (or at best is very opinion based) and as a matter of proof, I wanted to show you that other concepts (like 'cells') could equally be called building blocks of an organism. $\endgroup$
    – Remi.b
    Oct 11, 2016 at 20:09
  • $\begingroup$ In between your post edit and your comment you seem to both much the clarification I tried to do on your sentences. You might be well aware of some of the things I tried to clarify and this is ok. The most important is to know whether your question was answered and if not, why. (In any case, I would recommend you waiting for answer or peer-review from other users before accepting an answer). $\endgroup$
    – Remi.b
    Oct 11, 2016 at 20:18
  • $\begingroup$ Ah! the cell comment makes sense then :) I was wondering about that! yeah, sorry. I must have missed your edit. I try accept answers once there is more than one answer as I find the ticked answer prevents users from attempting an answer. $\endgroup$
    – EveryBitHelps
    Oct 11, 2016 at 21:19

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