Basics of Molecular Biology. Central Dogma: - DNA replication - Transcription - Translation Metabolic regulation: - Genetic level - Metabolic pathway control. Central Dogma. Central Dogma: universal - is stored on the DNA molecule.
- DNA replication
- Genetic level
- Metabolic pathway control
Central Dogma: universal
- is stored on the DNA molecule.
- : 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.
mitotic (M) phase
Cell Division Cycle (Mitosis)
The primary product of transcription:
m-RNA, t-RNA and r-RNA.
Transcription requires: RNA polymerases
e.g. ATP, GTP,
The base-sequence of RNA is the precise complement .
DNA template RNA product
The sigma factor of RNA polymerase recognizes a specific sequence of nucleotides on a DNA strand – promoter region.
the strands unwound.
Transcription starts with the core enzyme of the RNA polymerase then the sigma factor is released.
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.
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.
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.
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.
Translation consists of Initiation, Elongation and Termination.
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 (N-formyl)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.
e.g. phosphorylation catalyzed by enzymes such as with kinase.
(e.g. phosphorylated TP53 protein functions as tumor suppressor).
components, processes, features