Our incredibly complex design
The Human Genome Project predicted about 20,000 proteins in humans, based on the number of genes in the DNA sequence. About 90% of these have been found. However, the number is likely much, much greater than that. This is because the information in one ‘gene’ can be used in many different ways to generate many different proteins.
For example, genes comprise of segments called exons separated by introns. The protein-manufacturing machinery can mix and match which exons it uses to generate many different protein variants. Machines can also edit proteins after they are made—e.g. insulin comes from cutting a section out of a longer protein.
All this is highly controlled by sophisticated programs that decide which protein variants, and how many, to make in every cell of the body. There are hundreds of cell types, each producing different unique sets of proteins. And some of them are only produced at specific times and places.
So, how many proteins can human cells make? In short, no one knows. Some estimate there are millions. Dr Lydie Lane of the SIB Swiss Institute of Bioinformatics says, “there could be millions of varieties of proteins inside each of us, all coming from the same 20,000 genes” and “We don’t have the means to know how many there are, and when and why, etc.,” she says. “So this is quite dark.”
Scientists are only beginning to scratch the surface of the astounding functional complexity in the design of the human body.
- Howes, L., Many of our proteins remain hidden in the dark proteome, cen.acs.org, 24 Jan 2022.
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