The total number of nitrogenous bases in human genome is estimated to be about
(1) 3.5 million
(2) 35 thousand
(3) 35 million
(4) 3.1 billion
(4) The two DNA strands are held together by weak (hydrogen) bonds between the bases on each strand, forming base pairs. Genome size is usually stated as the total number of base pairs; the human genome contains roughly 3 billion base pairs.