Assuming the cow genome is 3 Gb109 base pair and the average

Assuming the cow genome is 3 Gb(10^9 base pair) and the average molecular weight of a base pair is 650 Dolton, how many cells did you have in the 0.1 ml cell suspension? Please show work

Solution

The average molecular weight of a base pair of DNA is 650 Dalton or 650 gm/mol. This is the molar mass or we can say that I mole of a bp of DNA weighs 650gm.

Therefore the molecular weight of any length of DNA (in base pair) can be calculated by multiplying the length into 650.

Given that the cow genome, or the amount of DNA contained in a cell, is of the length 3Gb =3 x10⁹ bp.

Thus, the molecular weight of this genome length of DNA = ( 650 x 3 x 10⁹ ) gm/mol = 1.95 x 10¹² gm/mol.

Hence, we can assume that 1 cell contains 1.95 x 10¹² gm/mol of DNA. Therefore, finding out how many such copies of DNA (genome size) are there in given sample, we can find the number of cells.

Concentration of DNA in given sample = 30 ng/ml

Since, sample size is of 0.1 ml, the sample mass of DNA contained = 3 ng

Number of such DNA (genome size) = (sample mass x Avogadro\'s number)/molar mass

= (3 x 6.023 x 10²³)/1.95 x 10¹²

= 9 x 10¹¹ approximately.

Therefore, there are approximately 9 x 10¹¹ cells in the given sample.