Litte Big Things

Last week we discussed DNA and how a majority of it is non-coding. I think an appropriate topic to follow would be what exactly does the coding DNA undergo to produce all the necessary proteins.

The process of turning the coding DNA genes into proteins is called the Central Dogma, and Francis Crick first introduced this concept in 1958. He stated,

" The Central Dogma. This states that once ‘information’ has passed into protein it cannot get out   again. In more detail, the transfer of information from nucleic acid to nucleic acid, or from nucleic  acid to protein may be possible, but transfer from protein to protein, or from protein to nucleic acid is  impossible. Information means here the precise determination of sequence, either of bases in the  nucleic acid or of amino acid residues in the protein. "

The basis of the Central Dogma is that DNA is replicated. Once the DNA is replicated, transcription occurs by replicating a DNA strand into messenger RNA. The messenger RNA then gets translated into proteins by having ribosomes read the codons in groups of three. This explanation is very general, and so much more happens within each step that allows the central dogma process to complete.

My favorite step of the Central Dogma is the way DNA replicates. The replication of the DNA is said to be the fundamental step in the central dogma. When DNA replicates, it first has to unwind from its double helix formation. This happens by using a helicase to also create a replication fork that hosts the initial copying. A daughter strand is created by reading the parent strand using DNA polymerase III to read the template strand starting from the 3 prime end to the 5 prime end. It also adds new complementary nucleotides from the 5 prime end to the 3 prime end of the daughter chain. DNA replication uses DNA polymerase I to remove RNA primers that are added at the start of the process and replaces them with DNA. Multiple fragments are made during the replication process and when the process is complete DNA ligase comes to join the fragments with phosphodiester bonds. This entire process takes less than an hour and multiple cells can replicate their DNA at the same time. That is why I find this part of the Central Dogma so interesting. The fundamental step of protein production can happen on the drive from Houston to Huntsville!