Question: How much dna is there in a person

Anthony Redmond answered on 16 Jan 2019:

You might read elsewhere that we have 3 billion base pairs (these are the letter [each is shorthand for a specific molecule] -pairs that make up the rungs of the spiral ladder of the DNA structure) of DNA in each cell, but actually we have 6 billion base pairs (half of which are unique), because there are two copies of each chromosome (males having X and Y chromosomes complicates this a little though!). Anyway. This amount of DNA has a mass of just over 6 picograms, and our bodies are estimated to have roughly 37 trillion cells! So, this works out at around 0.222g (for me at least) of DNA in a human. This amount seems tiny! But the length of all those bases added together would probably be a couple of times greater than the diameter of the solar system!

There are a few problems with this estimate though. First: not all cells have the same amount of DNA:
Our bodies also have cells with additional copies of all of our DNA (e.g. some form platelet cells in blood, which form clots to stop us bleeding), or without any genome (e.g. red blood cells specialised for oxygen transport).
Second: that count is only for human cells. and not all the cells in a person are human!!!
Some studies suggest that there are probably more cells from microbes, like bacteria, in our bodies than their are human cells! These simpler species usually have much less DNA than we do, but this varies a lot between different microbes, and different people can carry different microbes (and in very different amounts)!
So knowing how much DNA is in a person is pretty hard!