Can We Tell How Old DNA is?!?

Question

If you have a dna sample from semen for example, can we tell how old the semen specimen is? Does DNA erode over time?

Answer 1

DNA is a thin molecule that can break. A sperm is a very streamlined cell that has discarded almost everything organelle wise except for the DNA a burst of energy stored up to get it where it needs to go. If the sperm dies or gets too old... how will it repair itself? The DNA is not being regulated in that cell TO repair itself. It is set to save ALL the energy it can for transport.

You can look at the telomers in eukaryotic cells (of course a sperm is a eukaryote!) as they get shorter the more a cell divides (mitosis-speaking), however, since sperm don't divide, being mature cells (precurser cells to sperm divide like crazy though), looking at telomers will not work for you.

You could run PCR (polymerase chain reaction (think of a copy machine), making more copies of the sperm's DNA) provided you have the proper starter fragments of DNA (primers), to match in the wanted areas to look at as "primers" get get replication going. If the DNA has broken, the copies made with be much shorter than if the DNA was whole. The smaller the copies, the more breakage... a general reflection of the "erosion" you speak of. However, you must have a "control" (good, new sperm DNA) so you know YOU did not break the DNA while studying it but rather that happened during its aging.

If you don't want to look at DNA but rather something else... You could look at the enzymes in the tip of the sperm (the enzymes, for example with humans, needed to disolve the zona pelucida, the outer coat, on a mature oocyte (egg cell). You could run ezymatic activity testing (extract the enzymes, give them some material it will digest, see how able it is to digest it versus how able new sperm is at digesting it). You could look at the sperms outer membranes, proteins in the flagellum, etc. Electron microscopy, amoung many other techniques could help you out too. In terms of how many minutes/hours/days/whatever you want to calculate... well, I don't know how to do that.

Answer 2

DNA breaks down with time due to a number of factors, both chemical and physical. You would be hard-pressed to tell how old a DNA sample was simply based on how degraded it was, as there's just too much variability in how it has been treated and affected since it was 'produced'. Your best guess would still be a total guess.

Answer 3

I think you can....
You dna is made of proteins, so you have carbon in it...so i guess a C14 datation can work on it....

Answer 4

i think so