1953: James Watson and Francis Crick presents the DNA structure Basis: Maurice Wilkins and Rosalind Franklin’s X-ray crystallography images of DNA Watson, Crick and Wilkins – Nobel prize in Physiology or Medicine in 1962
Nucleic Acid Chemistry purine pyrimidine
Classes of RNA
The Central Dogma
DNA REPLICATION 1. Origin of DNA Replication
2. Unwinding of the DNA 3. Stabilization of the Y-junction 4. Polymerization of the nucleotides
5. Formation of the Leading and Lagging Strand 6. Formation of the Replisome 7. Replication of the Leading and Lagging Strand
Replication of the Lagging Strand
- enzyme primase provide the free 3’-OH group at the site of Okazaki fragment initiation in the lagging strand
Primer Removal and Gap Filling
8. Primer Removal and Gap Filling 9. Ligation
Ligation- the polymerase cannot attach together the fragments, the enzyme DNA ligase completes this task by making a phosphodiester bond
DNA TRANSCRIPTION (Prokaryotic)
1. Initiation of Transcription
TATAAT known as Pribnow box
It begins 6 to 8 nucleotides down from the Pribnow box.
Uses the DNA coding strand.
First base to be transcribed is noted as +1.
terminator sequence or stop signal
stem-loop structure is formed which causes the RNA polymerase to pause which may then allow termination to occur under two different circumstances.
Rho dependent termination
Rho independent termination
1. Initiation of Transcription 2. Polymerization
The lactose operon promoter and its consensus sequences. The start point for RNA synthesis is labeled 1. The region around 35 is the site at which the RNA polymerase first attaches to the promoter. RNA polymerase binds and begins to unwind the DNA helix at the Pribnow box or RNA polymerase binding site, which is located in the 10 region.
Reading Frames and Their Importance
The place at which DNA sequence reading begins determines the way nucleotides are grouped together in clusters of three (outlined with brackets), and this specifies the mRNA codons and the peptide product. In the example, a change in the reading frame by one nucleotide yields a quite different mRNA and final peptide.
takes place in the ribosomes
ribosome is composed of a small sub-unit and large sub-unit
uses the genetic code
is a series of codons that contain the triplets of bases in the DNA and mRNA. Several mRNA codons may code for a single amino acid (degeneracy of code).