Question

You are purifying bacterial chromosomal DNA to send off for genome sequencing. The estimated genome size of your organism is 4 Mbp and you know that the average MW of a base pair is 660 Daltons. You have isolated 1 microg of genomic DNA, how many moles of DNA are in your sample? If you resuspended the chromosomal DNA in 50 microL, what would be the final concentration of the DNA?

Answer 1

1 Daltons means 1g/mol.

Hence 660 Daltons means 660g/mol. We have 1ug of DNA samples. That means,

660g =1 M

1ug =?

= (1×10^-6)/660 ( converting ug into g)

= 1.51 nM, is the moles of DNA present in the sample.

Now 1ug of DNA is resuspended in 50ul, that means concentration is 1ug/50ul.

If we convert it into litres the concentration would be 20mg/1lt.

We know that 660g/lt becomes 1M.

So accordingly,

= (20×10^-3)/660 (converting mg into g)

= 0.030×10^-3 M

= 0.030 mM is the concentration of DNA is moles.