This is number 5 in the new Questions you never asked, but now that I mention it, yeah, that's a good point series.

So, although you probably never thought about it, now that I mention it, yeah, that's a good point. How many genes do we have?

I think before i answer this, think for a second about how complex we are (or how complex you think we are), and give an approximation of how many genes you think we need to produce the living thing we call humans. Now you can compare it with the real answer: 30,000.

Well, approximately 30,000, anyway. Not all the genes are known, as yet. This is because it's extremely difficult to read genes from DNA. About 99% of the DNA is 'junk DNA', i.e. not genes. this means that it doesn't code for proteins, and doesn't really do much at all. So trying to find which parts of the DNA are genes and which aren't is like this: imagine that i take a Dostoyevski book, in russian (assuming you don't speak Russian), and throw in 100 times more letters than there are in the book, semi-randomly (you have to figure out the patterns of my randomness). Now try to figure out what the original book was (note you don't speak russian - you don't know what are words and what aren't). Now do it blindfolded.

So all we have is about 30,000 genes in our DNA. These, incidentally, code for approximately 100,000 proteins. So each gene codes for, on average, 3 proteins. (In one known case, a gene codes for 64 proteins). This is done by all sorts of neat dna tricks, such as inclusion or exclusion of an exon (part of the gene that actually codes for proteins) for different proteins.

For a long time scientists believed that we need about 80,000 - 100,000 genes, but it turns out that we have only about 2 fruits flies' worth of genes.

For comparison:

Actually, it is interesting to note that the difference between human DNA and chimp DNA is about 1%. And not one gene has been found in humans and not in chimpanzees.

ariels wishes it to be known that the 30K number you see thrown about doesn't take into account alternative splicing . Whether variants are different genes or not is open to question , of course.

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