> How many nucleotides are in human DNA?
> And, is the number of nucleotides in human DNA constant across humans
> Is that number close? 6 billion? Or are there much more or much less?
> I read in a book that there were 200,000 genes in human DNA, and it said
> 1000 nucleotides per gene, which has to be an approximation, right? Since
> nucleotides gives you an amino acid, wouldn't the number of nucleotides
> gene have to be evenly divisible by 3?
>> But by that calculation, 200 million base pairs approximately in a human
The correct size of the human genome is 2.8 bilion base pairs (two
Your calculation assumes that the DNA only consists of genes, like pearls
a string, which is not correct.
Yes, the number of base pairs that encodes the protein is divisible by 3.
>> How do we know that introns are non functional? Introns exist within a
> gene, right?
All we know is that they don't encode the final protein, as they are
spliced out of the messenger RNA, than encodes the protein.
> Not junk outside of start and stop codons, right?
No, it's inside the start and stop codon.