Can DNA of a person change along with time?

Question

Currently there is a heated case in Malaysia. The DNA sample of the accused had been taken 10 years ago but the police demanded that they need a fresh sample as the old sample is too old and this is said by the Prime Minister. Do you need a fresh sample each time for a genetic fingerprinting? I had the opinion that a report of the DNA test is sufficient to validate the DNA sample retrieved from the body of the accuser. All the doctors an scientist please correct me if I am wrong. Thank you.

Answer 1

The issue here is not to do with the DNA changing - but to do with quality. DNA degrades over time through a variety of chemical processes and you may end up with a sample that is of poor quality - lots of short fragments, or quantity.

This is not ideal for creating a profile, as you may get inaccurate results.

Commonly, you get  'allelic dropout' where you lose one allele in a heterozygote but you may also get extra peaks occurring from non-specific amplification of DNA fragments.

That is why it is better to have a fresh sample wherever possible.

Answer 2

I am a biologist so I have some knowledge pertaining to DNA (although not an expert!).

I think one question regarding this case is the condition of the sample lifted off of the victim. If the authorities were to use the old DNA samples, we would know. If the old samples were somehow planted on the victim, we would also know. There are various tests that can assess the rate of degradation of the sample and conclude the age of the sample. Its quite predictable, in my opinion, because DNA is sensitive to various environmental effects, such as heat, UV (from the Sun) and chemicals (such as detergents etc.)

The human genome has billions of base pairs (the basic chemicals that provide the "fingerprint") and the authorities could use various "loci" on the DNA match the samples.

Answer 3

DNA does change in that each time a cell divides, it picks up mutations, most of which have no effect on the organism.  It is unlikely, however, that such a change would have an effect on a DNA test of the type you are talking about.  Most of these tests are done by analyzing the fragments produced after digestion of the DNA with enzymes (the frags are called RFLPs).  Since many RFLPs are analyzed, it is almost impossible for the DNA to cange sufficiently to give incorrect results.

Answer 4

The age of sample provided is / are of no important.

The degrade is/are only on the material or sample itself, however this do not and will not change nor alter DNA patterns.

Example- tissues and blood will degrade/rot over a period of few hours/days/weeks/months and years.

Materials will and do rot, but not the DNA.

One may picks up some fragments of bones,nails,hair from a 5000 year old mummy and the DNA can still be extracted. It even tells the blood group as well as approximate age of the sample

Your fingerprints or thumb prints are only good when the skin are in good condition before death.

As the body/skin starts to rot or decompose.

But DNA in the bones , dried skin,dried blood, nail , hair remains the same even after centuries.

As such there is no need for any "fresh" DNA.

You did mentioned "sample too old ".

Meaning DNA test was done.Meaning there was a lab test.

And all DNA lab test do have datas/records of the said previous test.This also means there are copies or readout provided for the court / forensic / attorney / police / accuser and defender.  

So many copies there, all went missing?

I did read the Anwar latest case,

I think Anwar should not provide his blood but samples of his finger nails instead.

Lets see if Malaysian police will go as far as  "planting" Anwar's fingernails up the 'victim's" corn hole.

This was , they have to change the charge from "sodomy" to "fingering".

I think your PM said he himself is too old or was the dna too old?

Is he himself an expert? or at least a doctor?

From the way your PM Datuk Sri Haji Abdullah bin Haji Ahmad Badawi answered, i do think he is a great remarkable moron.

Answer 5

The old sample might have degraded, such that they can't test it, but If you did a DNA test on you now, and did another one 10 years ago, the two results would be the same.

The only reason the request woud be legit is if they took the sample, but didn't actually test it, or if they want to do a different test than the previous one.