Question

Calculate the weight of DNA (in grams) contained in the nuclear genome of a human sperm cell. Assume the G/C content is 41%. Show your calculations.

Answer 1

The estimated nuclear haploid size of human genome is 3,031,042,417bp for X gamate and 2,932,228,937bp for Y gamate.

Relative molecular mass of A/T = 615.383 and G/C = 616.3711

Mass of A/T bp = Relative molecular mass of A/T x Atomic mass unit (in picograms)

                       = 615.383 x 1.660539 × 10⁻¹²

                        =1.021867x10^-9pg

Mass of G/C bp = Relative molecular mass of G/C x Atomic mass unit (in picograms)

                        = 616.3711 x 1.660539 × 10⁻¹²

                               =1.023508x10^-9pg

Based on this data, and the given assumption that G/C content is 41%, the weight of DNA (in grams) can be calculated as follows:

For X gamate, weight of DNA = [%G/C content x Mass of G/C bp + %A/T content x Mass of A/T bp ] x size of genome

                                           = [0.41x1.023508x10^-9pg + 0.59x1.021867x10^-9pg] x 3,031,042,417

                                           = 1.022539x 10^-9pg x 3,031,042,417

                                           = 3.099359 pg

                                           = 3.099359 x 10^-12g   (1pg= 10^-12g)

For y gamate, weight of DNA = [%G/C content x Mass of G/C bp + %A/T content x Mass of A/T bp ] x size of genome

                                           = [0.41x1.023508x10^-9pg + 0.59x 1.021867x10^-9pg] x 2,932,228,937

                                           =1.022539x 10^-9pg x 2,932,228,937

                                           = 2.998318 pg

                                           = 2.998318 x 10^-12g   (1pg= 10^-12g)