Protein Power: Transcription
Everyday Einstein looks at different kinds of RNA and how our cells use them to make proteins.
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A few weeks ago, in the episode called The Secret Life of Genes, I talked about...the secret life of genes.
In case you haven't listened to that episode (and you should!), in it we met Addy, the nucleotide. Addy had a job he loved - helping transcribe DNA into messenger RNA, (or mRNA), the code that tells the cell how to build proteins.
In last week's episode called Protein Power: DNA vs. RNA, we looked at RNA and how it differs from DNA. Make sure to check that one out too.
Today we’ll look at a couple of different kinds of RNA, and how the cell uses them to make proteins.
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When we last left our story, the RNA polymerase II enzyme had just finished making a copy of the gene by sticking a bunch of nucleotides together to form RNA. Well, now things really start to get interesting!
From Genes to Proteins
As I mentioned last time, RNA, or Ribonucleic Acid, comes in lots of different varieties. One of the kinds we need in order to make proteins is mRNA or, “messenger” RNA.
When RNA polymerase first creates the chunk of RNA needed to make a protein, it’s called pre-mRNA or precursor-mRNA. Before it can go on to be used to make a protein, however, a few more steps have to happen. To understand why, let’s take a look at some statistics.
For a long time, scientists thought that every gene contained the instructions for exactly one protein. Then, after the human genome was sequenced, we discovered that the human genome only has about 21,000 different protein-coding genes, while there are somewhere between 250,000 and 1,000,000 different proteins created in your cells. So what’s going on? The answer to this mystery is something called "alternative splicing."
When RNA polymerase first creates the chunk of RNA needed to make a protein, it’s called pre-mRNA or precursor-mRNA.
Your genes actually contain two different types of DNA sequences: exons and introns. For the most part, exons are the parts of the gene that contain the protein sequence, while Introns are extra bits of DNA stuck in between the exons. In order to get the real protein sequence, your cells send in special proteins to cut out the introns and splice the exons back together.
For example, if I give you the instructions, “Go to the park CHEESE and play PICKLES football.” The words, “cheese” and “pickles” are like introns. We need to splice them out to get a sentence that makes sense. For a long time, scientists thought that these introns were just leftover relics of evolution, chopped out and discarded. However, recent research has shown that many introns actually play important roles in the regulation of our cells.