Reviewing central dogma of molecular biology

1. Lab.1 Molecular Techniques/Practical 06/10/2015
Asst. Lecturer: Fairuz H. Abdullah
Reviewing Central Dogma of molecular Biology
DNA replication
DNA replication is a process in which copies of DNA molecules are produced within
the cell nucleus. This replication process is vital because it facilitates the transfer of
genetic information from one generation to another. DNA possesses the genetic
information for the cell, and DNA replication process just helps in duplicating this
information, so that the information transfer continues from generation to generation.
DNA Replication involves:
Initiation
1. Initiator proteins bind to oriC and cause a short section of DNA to unwind.
2. Helicase and other single-strand-binding proteins (SSBP) attach to the
polynucleotide strand.
3. The enzyme DNA gyrase, a topoisomerase, removes a twist in the DNA and
reduces the supercoiling.
Elongation
DNA polymerases synthesizes nucleotide strands by adding new nucleotides to the 3`
end of growing DNA molecules.
Termination
Replication finishes when the two replication forks meet at the terminus of the
chromosome.
Transcription
Initiation
In bacteria, transcription begins with the binding of RNA polymerase to the promoter
in DNA.
Elongation
One strand of the DNA, the template strand (or noncoding strand), is used as a
template for RNA synthesis. As transcription proceeds, RNA polymerase traverses the
template strand and uses base pairing complementarity with the DNA template to
create an RNA copy. This produces an RNA molecule from 5' → 3', an exact copy of
the coding strand (except that thymines are replaced with uracils, and the nucleotides

2. Lab.1 Molecular Techniques/Practical 06/10/2015
Asst. Lecturer: Fairuz H. Abdullah
are composed of a ribose (5-carbon) sugar where DNA has deoxyribose (one less
oxygen atom) in its sugar-phosphate backbone).
Termination
Bacteria use two different strategies for transcription termination. In Rho-independent
transcription termination, RNA transcription stops when the newly synthesized RNA
molecule forms a G-C-rich hairpin loop followed by a run of U.
In the "Rho-dependent" type of termination, a protein factor called "Rho" destabilizes
the interaction between the template and the mRNA, thus releasing the newly
synthesized mRNA from the elongation complex.
Translation
Messenger RNA functions as the template for protein synthesis; it carries genetic
information from DNA to a ribosome and helps to assemble amino acids in their
correct order. Both prokaryotic and eukaryotic mRNAs contain three primary regions.
The 5` untranslated region, in bacterial mRNA, this region contains a consensus
sequence called the Shine-Dalgarno sequence, which serves as the ribosome binding
site, the protein-coding region, and the 3` untranslated region (3` UTR). tRNA is
involved in the translation of the nucleic acid message into the amino acids of
proteins.
Initiation
During initiation, all the components necessary for protein synthesis assemble: (1)
mRNA; (2) the small and large subunits of the ribosome; (3) a set of three proteins
called initiation factors; (4) initiator tRNA with attached methionine and (5)
guanosine triphosphate (GTP).
Elongation
In elongation, amino acids are joined to create a Polypeptide chain.
Termination
Protein synthesis terminates when the ribosome translocates to a termination codon.