Life: DNA – Translating Life

This is probably all the basic understanding of DNA that you will ever need (especially if you are a non-scientist). If you are a molecular biologist, than this is just the beginning!

Turning DNA into proteins (and thus creating life) is split into two distinct steps:

  1. Transcribing. (Meaning to write out)
  2. Translating. (So translating the written out code into proteins)

Lets start.

Transcribing:

Hang on to this as it is a bit odd.

Remember nucleotides and codons? Well one special fact about these nucleotides is that they are always found in pairs. Not only are they found in pairs, but always the same pairs. For example A (Adenine) always pairs with T (Thymine) whilst C (Cytosine) always pairs with (Guanine). In biology this is called complementary. A is complementary to T and C is complementary to G. Let us illustrate:

Some DNA

Ignore the curling bits, and look at the lines in between. Note how there are four different coloured lines? Each of those colours represents a nucleotide. So imagine cyan is A and orange is T, whilst purple is C and green is G.

Therefore each nucleotide pairs up with a nucleotide on the other side. Sorry if I’m drilling you about this too much. But it is really important for the next bit.

Prepare yourself for this:

When we transcribe DNA two things happen. If you see the picture above, and again look at the different coloured lines, the first thing that happens is DNA ‘unzips’ or essentially splits in half, right down the middle of those lines. This exposes the nucleotides to the rest of the cell.

It is when this happens that a special protein attaches to these bare nucleotides and starts to ‘transcribe’.

This means that this protein slides down the open DNA and makes a near carbon copy of the DNA. There are however 3 differences:

  1. It does not make a carbon copy of DNA, but instead makes a copy called RNA (this will only last for a small amount of time and is more moveable, whereas DNA will stay in the nucleus and remain for the cells entire life).
  2. This RNA is complementary, it is an exact opposite of the side that is being transcribed (C’s are turned into G’s etc). However:
  3. Here’s the odd bit. There is no such thing as Thymine in RNA. Instead they have Uracil (now know as U). Therefore any A’s are not transcribed into their normal complementary T, but instead to RNA’s complementary U.

For some reason scientists like to organise amino acid codons into the RNA ones after transcription. So I can now present you with the full table:

The 3 letter abbreviations are defined in the post linked at the top.

After the protein has gone far enough down the DNA, and reaches a ‘stop’ codon, it will stop and detach, allowing DNA to zip back up.

What are we left with? A piece of RNA that is complementary to some part of the DNA. There are extra bits added on, to make sure it isn’t eaten by the cell, and is then transported out of the nucleus into the R.E.R. remember that?

Next part.

Translation:

So now the RNA has entered the R.E.R. and is latched onto by a ribosome (found all over the R.E.R.)  curiously, ribosome’s are made of RNA themselves.

Once attached the ribosome starts to move up the strand of RNA, ‘reading’ the code of the nucleotides. As it goes it collects amino acids from the surrounding R.E.R. and starts putting them together.

It’s like Lego (again) when you have a massive building to make. You read the instructions, then while you do that you put the bricks together. Once you’ve finished reading the manual you will (hopefully) have a Lego house. In the cell, you will have a fully formed protein.

That in a nutshell is protein synthesis.

The end.

That wasn’t so hard was it?

Conclusions:

  • Transcription is turning a section of DNA into a string of complementary RNA (remember the uracil!)
  • This RNA is sent to the R.E.R.
  • There a ribosome will latch onto the RNA and create a protein from free floating amino acids.

Brilliant!

Here’s a complementary video to show you what you just learnt:

I wish there was a bit less talking and more action… But it looks pretty!

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1 Comment

  1. Life: In the Making… Fertilisation | Science Defined

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