Central Dogma:
- DNA replication
- Transcription
- Translation
Metabolic regulation:
- Genetic level
- Metabolic pathway control

Central Dogma: universal
molecule.
is stored on the DNA
: The genetic information can be replicated directly to form a second identical molecule.
: Segments information on the
DNA molecule can be transcribed to yield m-, t-
, r-RNAs.
: Using RNAs, this information is translated into proteins.

The primary product of transcription: m-RNA, t-RNA and r-RNA.
Transcription requires: RNA polymerases
- Growth of RNA polymers is energy requiring.
e.g. ATP, GTP,
The base-sequence of RNA is the precise complement .
DNA template
A
RNA product
U
T
G
C
A
C
G

Promoter
RNA polymerase
Operator Gene 1
DNA template
Gene 2 Gene 3 m-RNA http://www-class.unl.edu/biochem/gp2/m_biology/animation/gene/gene_a2.html

- Initiation:
The sigma factor of RNA polymerase recognizes a specific sequence of nucleotides on a DNA strand – promoter region.
the strands unwound.
- Elongation:
Transcription starts with the core enzyme of the RNA polymerase then the sigma factor is released.
- Termination:
RNA polymerase encounter a stop signal or transcription terminator (e.g. rho protein in procaryotes).
- the RNA polymerase dissociate from the DNA template
- the RNA transcript is released.

Translation is the final step on the way from DNA to protein.
- It is the synthesis of proteins directed by a mRNA template.
- The information contained in the nucleotide sequence of the mRNA is read as three letter words (triplets), called codons.
- Each word stands for one amino acid.
- During translation are linked together to form a chain which will later be folded into a protein.

Universal -letter codons on mRNA: A, G, C, U
- 64 codes for 20 standard amino acids
- more than one codon can specify a particular amino acids.
- Nonsense codons: UAA, UAG and UGA
- Do not encode normally for amino acids.
- Act as stop points in translation.
- encoded at the end of each gene.

Important Components:
R :
The ribosome is the cellular factory responsible for the protein synthesis.
It consists of two different subunits, one small and one large and is built up from rRNA and proteins.
Inside the ribosome the amino acids are linked together into a chain through multiple biochemical reactions.

t-RNA:
The charged t-RNA (aminoacyl-t-RNA) carries an amino acid at one end and has a triplet of nucleotides, an anticodon, at the other end.
It is formed by the energy from two phosphate bonds and enzymes (aminoacyl-t-RNA synthetases)
The anticodon of a t-RNA molecule can basepair, i.e form chemical bonds, with the m-RNA's three letter codon.
The t-RNA acts as the translator between m-RNA and protein by bringing the specific amino acid coded for by the m-RNA codon.

t-RNA

• m-RNA template
• The translation process also involves a large number of protein factors that facilitate binding of mRNA and tRNA to the ribosome.
• Protein synthesis consumes a large part of the energy produced in the cell.

Translation consists of Initiation, Elongation and
Termination.
http://www.phschool.com/science/biology_place/biocoach/translation/init.html
Initiation results in the formation of an initiation complex in which the ribosome is bound to the specific initiation (start) site on the mRNA while the initiator tRNA charged with (Nformyl)methionine is annealed to the initiator codon and bound to the ribosome.
- Protein synthesis begins with a AUG codon (less frequently
GUG) on the m-RNA
AUG encodes for a modified methionine, N-formylmethionine
(fMet).
In the middle of protein, AUG encodes for methionine.

Elongation joins amino acids to the growing polypeptide chain according to the sequence specified by the message.
- The formation of the peptide bond between the two amino acids occurs on adjacent sites on the ribosome: the P or peptidyl site and the A or aminoacyl site.
- The growing protein occupies the P site, while the next amino acid to be added occupies the A site.
- As the peptide bond is formed, the t-RNA associated with the P site is released. http://www.phschool.com/science/biology_place/biocoach/translation/elong1.html

Termination
- At a stop codon, a release factor reads the triplet, and polypeptide synthesis ends.
- the polypeptide is released from the tRNA.
- the tRNA is released from the ribosome, the two ribosomal subunits separate from the mRNA.
http://www.phschool.com/science/biology_place/biocoach/translation/term.html

• Posttranslational modification means the chemical of a protein after its translation. It is one of the later steps in protein biosynthesis.
• It may involve the of a proper structure, the formation of disulfide bridges and attachment of any of a number of biochemical functional groups, such as phosphate, acetate, various lipids and carbohydrates.
e.g. phosphorylation catalyzed by enzymes such as with kinase.
(e.g. phosphorylated TP53 protein functions as tumor suppressor).

• DNA replication
• DNA-RNA transcription
• RNA-Protein translation
• Posttranslation components, processes, features