According to this paper you might expect 1ug of dna from 20mg of nail clippings,

Article High-Quality DNA from Fingernails for Genetic Analysis

The amount that you can see depends on many factors like number of bands, distance run, well size, size of dna and dna stain used but as you are measuring genomic dna there are no bands just a smear of all sizes so even large amounts of dna may not be visible. I would expect to see a band of about 500picogramme but in a smear many times that will not be visible.I would not bother with visualisation but take a sample and a primer pair that always works and see if you get amplification. If you are precipitating dna then use a co precipitant like linear acrylamide or glycogen to increase yield and if using columns do a second elution off the membrane with hot elution buffer and add it to your first eluate to maximise yield

which extraction kit did you use?

Please check this short communication.

Genetic identification of decomposed cadavers using nails as DNA source

Author links open overlay panelM.AlloucheabM.HamdoumaP.ManginbV.Castellab

https://doi.org/10.1016/j.fsigen.2008.07.008

They use a previous wash with absolute ethanol and then they use a lysis buffer and they are purified with QIAamp DNA mini kit (QIAGEN) columns.

Paul Rutland

i don't understand this " but as you are measuring genomic dna there are no bands just a smear of all sizes so even large amounts of dna may not be visible. I would expect to see a band of about 500 picogramme but in a smear many times that will not be visible."

we don't see even just a smear,, there was no DNA bands at all except for DNA ladder

For other suggestions, thank you.

Roy Rodriguez-Hernandez we used thermo fisher scientific kit

Thanks for your advice in the next comment.

hi Marwa H.Elsharkawy ,

what i meant was that a small amount of dna concentrated in a thin band may be visible generally but I agree that your dna is a mixture of every size due to degradation of the dna so is smeared over a few centimetres of the gel so no part of the gel track has very much dna in it so that the dna will not be visible at all. Sorry that was not clear...I agree you are not expecting to see a band and that is correct.

Paul Rutland I like the paper you provided. I always thought that fingernails are a 'dead' part of our body. I did not know there are so much gDNA can be extracted from fingernails. Fingernails usually are preserved when a person dies. I wander a similar amount gDNA can be extract from a decayed and dried body (dead many years)!?

Marwa H.Elsharkawy

There is a similar question asked in another thread on RG: " What is the minimum DNA quantity (ng) required to visualize DNA on Agarose gel? " See below link.

By the way, did you grind the fingernail samples to fine enough? It is hard to grind fingernails I guess.

Link: https://www.researchgate.net/post/What_is_the_minimum_DNA_quantity_ng_required_to_visualize_DNA_on_Agarose_gel#:~:text=Seeing%2010%20ng%20DNA%20in,to%20be%20produced%20during%20electrophoresis.

hi Yuan-Yeu Yau decay is the real problem when it comes to isolating good dna. Age less so and the length of the amplimer is very important as the age and decay shorten the strand average length of the dna,

I have amplifies short amplimers looking for mycobacterium bovis and , M Leprae

isolated from bodies from between 4th century BCE and 4th century AD and plasmodium species in Egyptian mummified bodies and got sequenceable amplimers on bands of less than 140bp and these amplimers are from a minority dna present in the body so human dna will not be a problem

Ahmed Adel Aboushanab I mean by " samples concentration by nanodrop were non-relevant" that the 40 samples concentration are non relevant (6.5 ng, 40 ng and even 583 ng!!) for example

260/280 ratio range from 1.3 and 1.4 in most samples, only two samples gave 1.8 and 1.9 respectively.

concentration of gel was 1%,

Marwa H.Elsharkawy ,

As Ahmed Adel Aboushanab mentioned, NanodropTM measurement result can give you the quality (purity) and quantity of your isolated DNA. So, what is your NanodropTM results anyway? You did not mention it in your question.

ok, now I saw your post of your Nanodrop results. We posted almost at the same time.

Yuan-Yeu Yau i can't mention all measurements for 40 samples BUT as i said,

for 3 samples, conc were 6.5 ng, 40 ng and even 583 ng

260/280 ratio ranges from 1.3 and 1.4 in most samples, only two samples gave 1.8 and 1.9

As I expected, the fingernails (which we cut down) is a dead tissue (Link below).

" Your visible nails are dead. As new cells grow, they push old ones through your skin. The part you can see consists of dead cells. That's why it doesn't hurt to cut your nails. " ( https://www.healthline.com/health/beauty-skin-care/what-are-nails-made-of#1 )

Paul Rutland Thank you for sharing the story with us. So, when you were looking for Mycobacterium bovis and M. Leprae in Egyptian mummified bodies, did you collect multiple tissue samples for PCR amplification from a body, or only collect 1 sample from a specific tissue?

Yuan-Yeu Yau what is the problem if they are a "dead tissue"?

they extract DNA from mummified bodies and it works

can u give me further explanation?

Marwa H.Elsharkawy There should be no problem for isolating DNA from dead tissues, as many forensic scientists already isolate DNA from dead bodies for PCR and crime investigation. I just curious, we can get 1 ug DNA from only 20 mg of fingernails (dead tissues), as mentioned by the paper posted by Paul Rutland .

By the way, the 'unit' you gave, " conc. were 6.5 ng, 40 ng and even 583 ng ", is not concentration unit. Is that number 6.5-40-583 from 'total DNA' or 'DNA concentration'? Concentration units are ex. ng/uL or ug/uL or ng/mL or ug/mL....I guess yours should be ng/uL. So, how much (uL) did you use for running gel? If you gave the number, then we can calculate how much 'ng' of DNA you have loaded into each lane. Many people suggest 10 ng as the minimum amount of DNA you can see on a EtBr gel. So, If you have 20 ng in each well, it should have no reasons not to see the band (in normal situation).

I know conc should be ng/uL but i just can't write (uL), we loaded 10 uL DNA + 2 uL loading dye.

Hi Yuan-Yeu Yau

The egyptian work (c700bCE) was for plasmodium species and we multiple sampled only bone tissue to get the dna. The question regarding dead tissue is slightly complex ,I think, Of course dead meat etc gives perfectly good dna and trapped cells in the nails seem to do so as well. One minor problem can be dead skin cells as in dandruff where as the cells die I think that some of the dna is broken down for recycling but it does not make very much difference since even a few cells when amplified with 30 cycles of pcr will give visible amounts of amplimer

Marwa H.Elsharkawy , so you have 6.5, 40, 583 (ng/uL), 3 example samples. You used 10 uL each for running gel. In other words, you had 65 ng, 400 ng or 5830 ng (=5.83 ug) in 3 lanes in the gel. Are you sure the unit is ng/uL? Not ng/mL? If ng/uL, one sample you loaded in the gel well was around 5.8 ug of DNA. That's way too much. Are you sure?

It's ng/mL sorry, I am just exhausted nowdays.

Ok, good. Now, you have 6.5, 40, 583 (ng/mL) samples. And, you used 10 uL for running gel. Therefore, you had such amount of DNA in the gel lanes: 6.5 ng/ml x 10 uL = 6.5 ng/1000 uL x 10 uL = 65/1000 ng = 0.065 ng. Another 2 samples: 0.4 ng and 5.83 ng.

For using 0.065 ng, 0.4 ng, and 5.83 ng (all < 10 ng) to run gel, probably you won't see a band.

How much DNA sample (volume) you have for each of these 3 samples. How much fingernails did you use for genomic DNA isolation? Marwa H.Elsharkawy

I don't understand the first one

The second we used 20 mg of fingernails

Marwa H.Elsharkawy The first question I asked was: after you eluted DNA from the kit column into the eppendoff tubes (final step) for collection and storage for future use. How much (approximate volume) did you collect? If you have the number, we can calculate how much total DNA you have isolated from 20 mg fingernails.

For kit method, 50 uL was obtained

For organic method, we resuspend the pellet in 50 uL 1X TE buffer

OK, so you have 50 uL stock DNA solution for each sample, and you measured these samples with concentration of 6.5, 40, 583 (ng/mL). Assuming you did not dilute the stocks before Nanodrop measurement, then you obtained 6.5 ng/mL x 50 uL = 0.325 ng (total DNA) from 20 mg fingernails. The other two: 2 ng and 29 ng (total DNA) from 20 mg fingernails. The paper says that you can get up to 1 ug (=1000 ng) from 20 mg fingernails. That means that you got very few DNA from the extractions. Did you grind your fingernail samples very well? If not, the cells were not broken and DNA were not released as expect. Marwa H.Elsharkawy

you can elute your dna at the last step in 10 ul instead of 50ul it will increase your dna concentration ,also try to increase the percentage of the agarose gel for more resolution

min amount of DNA (in a band, not whole genome prep) that can be seen on a gel is ~20 nanograms (see Maniatis book -1st edition). To evaluate how much genomic DNA you extracted agarose gel must not be used because genomic DA will not migrate into agarose gel unless it is very fragmented (then you don't needed it). Use nanodrop, and if you dont have it, use old methods like Spectrophotometer. Do not use agarose gel

@Igor Nasonkin

"To evaluate how much genomic DNA you extracted agarose gel must not be used because genomic DA will not migrate into agarose gel unless it is very fragmented". I can't understand you, but many times we see DNA on gel in exact bands, can you clarify more?

Yuan-Yeu Yau Thank you, dear

Ahmed Adel Aboushanab Mohamed Halawa Thank you for ur answers

Genomic DNA will migrate into agarose gel from loading well. Intact DNA bands usually can be seen on the top of the gels. See attachments. (click to see the whole gel)

Attachment 1: blood genomic DNA

Attachment 2-3: plant gnomic DNA

Yuan-Yeu Yau I can conclude that here DNA is highly degraded and smeared. I noticed also bands travel down (not as another 2 pictures where DNA bands are intact, as u said can be seen on the top of gel), right?

Marwa H.Elsharkawy It has some degradation, but they were not highly degraded (judged from the picture). You can see the 'marker' lanes also have the 'gray' background. You know, when you take DNA gel pictures, you can adjust the camera to make the gel background brighter or darker. This picture the background was brighter. You can still use the gDNA to obtain some good experiment results.

Attached a picture. You can see what a 'highly degraded' DNA looks like on a gel. The DNA was degraded by sonication (from Qiagen; see PDF attached). Marwa H.Elsharkawy

Are you using usual DNA extraction kit or Prepfiler Forensic DNA Extraction kit ? As i see in the picture above, there is a problem with your protocol. For example if you use QIAamp DNA Mini Kit that is suitable for blood, body fluids, or washed cells from urine, ..., it's better to use a user-developed protocol available online at the manufacturer’s website for the tissue that you want to extract dna from.

Leila Hosseinzadeh Anvar i used usual DNA extraction kit

thank u for ur suggestion, dear

10ng