DNA holds the instructions When proteins are produced in the body, the instructions for how to make it comes from the DNA (deoxyribonucleic acid) BUT, there are many steps between a strand of DNA and a protein

Let’s review DNA first DNA is double-stranded Adenine is always across from Thymine Cytosine is always across from Guanine bases are held across from each other by weak hydrogen bonds A--T C--G

Making Proteins Making proteins involves another step as you saw on the first slide First, a molecule called RNA is produced This process is called TRANSCRIPTION

RNA Ribonucleic acid single stranded also made of nucleotides

The nucleotides of RNA They are slightly different than DNA They have a sugar and a phosphate group like DNA does

The difference Three of the nitrogenous bases are the same: Adenine (A) Cytosine (C) Guanine (G) The last one is different: Uracil (U)

Instructions for a Protein The instructions to make a certain protein are coded by the sequence of nucleotides in a strand of DNA (a gene) These instructions get transferred from the DNA strand to an RNA strand through transcription

So how does this happen? There are a number of steps in the process of making a protein The first involves two different parts: RNA polymerase the gene’s promoter A promoter is a certain order of DNA that acts as a “start” signal for transcription

RNA polymerase RNA polymerase is an enzyme It binds to the promoter of a gene This enzyme helps unwind and separate the two strands of DNA

The template One strand of the DNA acts as a “template” for making the RNA This means that the nucleotides that will form the RNA pair up with this strand RNA polymerase helps make this happen

Base Pairing Rules Just like with DNA, the nucleotides only pair with certain other nucleotides If there is a Thymine on the DNA strand, Adenine still pairs with it If there is an Adenine on the DNA strand, it now pairs with Uracil Cytosine pairs with Guanine just like before

Some covalent bonds are involved As the RNA nucleotides get added to the strand of RNA that is forming, they are forming covalent bonds The covalent bonds occur between the nucleotides of the RNA

How it ends Transcription keeps going until RNA polymerase reaches a “stop” signal on the DNA RNA polymerase falls off of the DNA and releases the RNA molecule The DNA then winds back up

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