Question

1.Each DNA base pair weighs, on average, 650 grams/mol. There are 3 billion base pairs in one haploid human genome. How much does one haploid human genome weigh? (Avogadro’s number is 6.02 x 10^23 molecules/mole)

2.How many human genome equivalents are in 20 ng of cfDNA?

Please show how you got to your answer

Answer 1

1) molar mass of a basepair= 650 grams/mol.

number of base pairs in the haploid genome= 310^9 bp

the molar mass of haploid genome= number of base pairs in the haploid genome molar mass of a basepair

= 310^9650

, = 1.9510^12 grams/mol

there are 6.0210^23 molecules in one mole

so the mass of a molecule= molar mass of haploid genome/number of molecules in one mole

   = 1.9510^12/6.0210^23

=3.2410^-12 grams

2) 1 ng= 10^-9 gram

so 20 ng= 2010^-9 g

=210^-8 g

number of genome equivalents in 20 ng= 210^-8 g/mass of a haploid molecule

= 210^-8 g/ 3.2410^-12

= 6172.8