Transcription and RNA Processing

ID #1157

How does the number of genes not equal the number of proteins? I think I'm confused on the connection...

It seems logical that if you can make 50 proteins, you need 50 genes to code for those proteins, right? In fact, this was assumed to be the case until we discovered alternative splicing. Using tropomyosin as an example, you can make 5 different types of tropomyosin -- and since the 5 types have different primary sequences, they are different proteins -- but you need only one gene to produce any of the 5. This explains why human cells are believed to make over 100,000 different proteins, but we've "only" discovered 25,000 or so protein-coding genes.

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