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RNA. The “other” Nucleic Acid. DNA is King! Absolute monarch! But, a King that is trapped within the castle – held prisoner. Besides, the King is far too valuable to go wandering about. DNA is KING.

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The “other” Nucleic Acid

Dna is king

  • DNA is King! Absolute monarch! But, a King that is trapped within the castle – held prisoner. Besides, the King is far too valuable to go wandering about.


Dna is king1

  • Although the King is held prisoner in the castle, he still must get his message out to all of his people. He still has a Kingdom to run, after all.


Dna is king2

  • If the King can’t leave the castle, but must run the Kingdom, how can he get his messages to his people? Issue his laws and orders? If he cannot come out, a MESSENGER must come in!


The king s messenger

The King’s Messenger!

Messenger RNA to the rescue! mRNA can enter and leave the castle freely, taking the King’s royal proclamations with him!

How does he remain undetected by the Castle Guards? He is smaller and only one-stranded! Very sneaky!

Royal proclamations

  • How does the Messenger know when the King needs him to come transcribe his message for the people?

  • The King puts out a sign that tells the Messenger that he has a Royal Proclamation for him to take to the people!

  • That sign is called a PROMOTER! When mRNA sees that promoter, he knows to come get the King’s message!

Royal Proclamations

Dna vs rna

RNA doesn’t have Thymine! Instead it has Uracil.

It is single-stranded!

In its sugar-phosphate backbone, the sugar is Ribose, instead of Deoxyribose.

DNA is found in the Nucleus, RNA is found in the cytoplasm


Rna as disposable dna

  • Think of Messenger RNA as a disposable copy of DNA!

  • mRNA will often copy a single gene in the nucleus, then take that gene out for translation into a protein.

  • mRNA begins transcription atregions of DNA called Promoters. Promoters tell mRNA where to start copying.

RNA as Disposable DNA


  • Remember that DNA Replication required the enzyme DNA Polymerase.

  • Transcription requires the enzyme RNA Polymerase!

  • RNA Polymerase binds to the DNA at the Promoter and separates the DNA strands!

  • The mRNA is then assembled using one of the strands as the template!


Rna editing

  • To temporarily return to the cheesy King metaphor again…

  • Let’s pretend that the King sends his signal to the Messenger to come pick up his Royal Proclamation and give it to the people.

  • However, when the mRNA picks up the royal parchment, it looks like it was written after the King had a few too many glasses of the Royal Wine.

  • There is, in fact, the Royal Proclamation, but there are also rambling sections that don’t make any sense and aren’t at all related to the King’s message to the people!

  • mRNA has to edit the message before giving it to the people, by taking out the nonsense parts.

RNA Editing

Rna editing1

  • The “nonsense” parts of the message are non-coding regions of DNA (regions that do not code for proteins).

  • These non-coding regions are called Introns

  • The parts of the sequence that DO code for proteins are called Exons

RNA Editing

Rna editing2

  • So, when the RNA molecule is formed (or transcribed from the DNA), both the Introns and Exons are copied from the DNA

  • But only the Exons contain instructions for assembling proteins in Translation

  • So before the mRNA will take the transcribed sequence to be translated into proteins, it has to be edited to remove the Introns

RNA Editing

The other rnas

  • mRNA has a hugely important job! It contains the genetic code!

  • mRNA transcribes the appropriate genes from DNA in the nucleus, edits the information to remove the unimportant stuff, and takes the gene to be made into a protein!

  • mRNA has a BIG job to do and it can’t do it alone, so it enlists the help of its sisters – Ribosomal RNA and Transfer RNA!

  • Messenger RNA (mRNA)

  • Ribosomal RNA (rRNA)

  • Transfer RNA (tRNA)

The other RNAs

The 3 rnas

  • mRNA- Contains the instructions for assembling amino acids into proteins

  • rRNA- The proteins are assembled on ribosomes

  • tRNA- Brings the appropriate amino acid to the ribosome, as specified by the mRNA

  • tRNA is what does the “translating” in Translation! It has an anticodon that binds to mRNA’s codon and drops off an amino acid there

The 3 RNAs

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