Once scientists found out more about the structure of DNA, they were able to learn how proteins were made. They realised that proteins were controlling what parts of the body did what, but they didn't know how the body knew. Obviously certain things are passed on genetically. the question is what enables these commands to survive generation after generation. Scientists have figured out that DNA is actually the blueprint for another molecule called RNA. RNA then carries out the commands and creates the proteins. This takes place in two steps, one called transcription, the other translation.

In this picture, the DNA molecule has once again split. However, in order to create RNA, only one strand is made. In this strand Uracil (U) matches with Adenine (A) instead of Thymine (T).

 

After the process of transcription the DNA zips up again and the RNA molecule has been created. The next step is translation. During this step, three different types of RNA work together to make put amino acids into a protein molecule. The proteins are then controlled by the genes to make the body work. (To learn more about genes, go to Genes: Size Doesn't Count). In effect, the messages encoded in th DNA which are passed on every time a cell reproduces end up controlling the genes that make us who we are. This is called "gene expression."

The first type of RNA, called mRNA or Messenger RNA, is translated into a sequence of amino acids which will make up the proteins. For this two happen, codons need to be formed. A codon is the sequence formed by every three nucleotides. (see image).

The sequence of bases in the codons determines what order the amino acids will be added to the protein chain.

 

In this picture we see the mRNA being created and the codons paring off. The circles on the end of the codon is the protein chain being created. For a closeup look at the genetic code click here. There are twenty amino acids. After transcription, the RNA leaves the cell's nucleus and enters the cytoplasm (see above image) . This is where the process of translation begins. The mRNA works with Ribosomal (r) and Transfer (t) RNA. The rRNA gives the code to start the protein sequence. After all the codons are put together following the instructions from the original DNA "blueprint," a "stop" codon is placed and the chain is complete. The new protein is released into the cell to do its job.