# Calculating moles from base pairs ??

• Author
Posts
• #16368
lulubell
Participant

Hi,
I’m trying to figure out the moles of a piece of DNA- using just the following information …..

The genomic DNA is 20000ng (mass) and is 15000 base pairs long

I know to get moles you have to do; Mass/ relative formula mass <— but I don’t know this….

Is it possible to do; mass/base pairs to get the number of moles?

In which case it would be 20000/15000 = 1.333 M ??

I then need to find the mass (in ng) in 1 mole- I know how to do this, but obviously if I get the first part wrong, my answer here will be wrong also

• #110670
JackBean
Participant

1500 bp is not molecular weight. For this you need average weight of nucleotide and with the number of nucleotides in molecule you calculate the molecular weight of the whole molecule. hat you use to calculate concentration.

But the concentration of DNA is usually in mass per volume (e.g. ng/ul).

• #111068
taruntbiotech
Participant

see this hope it will help u

Single-stranded: 330 grams per mole per base
330 (g/mol)/b
330 g / ( mol • b )

Double-stranded: 660 grams per mole per base pair
660 (g/mol)/bp
660 g / ( mol • bp )

Example problem:

Find the number of moles which compose a 1.5kb band whose mass was determined to be 120 ng (by gel comparison to standards).

(120 n g ) • ( mol • bp ) = 1.2E-4 nmol or 0.12 pmol
(1500 bp) ( 660 g )

• #111069
taruntbiotech
Participant

molbiol.edu.ru/eng/scripts/h01_07.html
also check this