DOGMA

1. Central dogma of molecular biologyCentral dogma of molecular biology
Meaning of Dogma
Dogma is the established belief or opinion held by
a religion, ideology or any kind of organization. it is
authoritative and not to be disputed
The Central Dogma of Molecular Biology
describe flow of genetic information

2.  first enunciated by Francis Crick in 1958first enunciated by Francis Crick in 1958
The central dogma of molecular biology deals with theThe central dogma of molecular biology deals with the
detailed residue-by-residue transfer of sequentialdetailed residue-by-residue transfer of sequential
informationinformation. It states that information cannot be. It states that information cannot be
transferred back from protein to either protein ortransferred back from protein to either protein or
nucleic acid.nucleic acid.
 In other words, 'once information gets into protein, itIn other words, 'once information gets into protein, it
can't flow back to nucleic acid.'can't flow back to nucleic acid.'
Central dogma of molecular biology

3. Central dogmaCentral dogma
The relationship of DNA, RNA and Proteins
DNA makes RNA makes Protein
Unidirectional transfer of Genetic information
DNA to RNA to Protein
 The organizing principle of Molecular Biology
Genetic information flows from DNA to RNA to Protein

4. 11 The DNA replicates its information in a process that involves manyThe DNA replicates its information in a process that involves many
enzymes:enzymes: replicationreplication
2 The DNA codes for the production of messenger RNA (2 The DNA codes for the production of messenger RNA (mRNAmRNA) during) during
transcriptiontranscription
33 In eucaryotic cells, theIn eucaryotic cells, the mRNAmRNA is processed (essentially byis processed (essentially by splicingsplicing))
and migrates from the nucleus to the cytoplasm.and migrates from the nucleus to the cytoplasm.
4 Messenger RNA carries coded information to ribosomes. The4 Messenger RNA carries coded information to ribosomes. The
ribosomesribosomes ‘read’‘read’ this information and use it for protein synthesis.this information and use it for protein synthesis.
This process is calledThis process is called translationtranslation
ProteinsProteins are involved in almost all biological activities, structural or enzymaticare involved in almost all biological activities, structural or enzymatic
Central dogma - represented by four major stages

5. 3 classes of information transfer suggested by the dogma
General Special Unknown
DNA → DNA RNA → DNA protein → DNA
DNA → RNA RNA → RNA protein → RNA
RNA → protein DNA → protein protein → protein

6. 3 classes of information transfer suggested by the dogma3 classes of information transfer suggested by the dogma
General Special Unknown
DNA → DNA RNA → DNA Protein → DNA
DNA → RNA RNA → RNA Protein → RNA
RNA → Protein DNA → Protein Protein → Protein
General transfers of biological sequential information

7. General transfers of biological sequential information - DNA to DNAGeneral transfers of biological sequential information - DNA to DNA
General
DNA → DNA
DNA → RNA
RNA → Protein

8. General transfers of biological sequential information - DNA to RNAGeneral transfers of biological sequential information - DNA to RNA
General
DNA → DNA
DNA → RNA
RNA → Protein

9. General transfers of biological sequential information - RNA to ProteinGeneral transfers of biological sequential information - RNA to Protein
General
DNA → DNA
DNA → RNA
RNA → Protein

10. Special transfers of biological sequential informationSpecial transfers of biological sequential information
Reverse transcription
Reverse transcription is the transfer of information from RNA to DNA (the
reverse of normal transcription). This is known to occur in the case of
retroviruses, such as HIV, as well as in eukaryotes, in the case of retrotransposons
and telomere synthesis.
RNA replication
RNA replication is the copying of one RNA to another. Many viruses replicate
this way. The enzymes that copy RNA to new RNA, called RNA-dependent
RNA polymerases, are also found in many eukaryotes where they are involved in
RNA silencing.[
Direct translation from DNA to protein
Direct translation from DNA to protein has been demonstrated in a cell-free
system (i.e. in a test tube), using extracts from E. coli that contained ribosomes,
but not intact cells. These cell fragments could express proteins from foreign
DNA templates, and neomycin was found to enhance this effect.

11. Special classes of information transfer RNA to DNARNA to DNA
Special
RNA → DNA
RNA → RNA
DNA → protein
Viral reproductive cycle (RNA-based)

12. Special classes of information transfer RNA to DNARNA to DNA
Viral reproductive cycle (RNA-based)
Special
RNA → DNA
RNA → RNA
DNA → Protein

13. Special classes of information transfer RNA to RNARNA to RNA
Special
RNA → DNA
RNA → RNA
DNA → protein
Viral reproductive cycle (RNA-based)

14. So the existence of RNA replication and
reverse transcription establish the general
principle that information in the form of
either DNA or RNA can be converted in
to the other type
DNA RNA

15. Single-stranded DNA was acting directly
as a template for protein synthesis.
Cell-free protein synthesis was measured
with extracts of E. coli strain K12
Denatured DNA as a direct template for in vitro
protein synthesis
Special classes of information transfer – DNA to Protein

16. Unknown genetic transformationUnknown genetic transformation
Unknown
Protein → DNA
Protein → RNA
Protein → Protein
There is no evidence so far that the sequence of amino acids
in a protein is translated by cell in to either DNA or RNA and
most likely such a translation may be non existent

17. Questions?Questions?
END

18. Prokaryotes Eukaryotes
1.All RNA species are synthesized by a
single RNA polymerase
1.Three different RNA polymerases are
responsible for the different classes of
RNA molecules.
2.mRNA is translated during
transcription.
2.mRNA is processed before transport to
the cytoplasm where it is translated.
Caps and tails are added and internal
parts of the transcript are removed.
3.Genes are contiguous segments of
DNA that are colinear with the mRNA
that is translated into a protein.
3.Genes are often split. They are not
contiguous segments of coding
sequences; rather, the codng sequences
are interrupted by intervening sequences.
4.mRNAs are often polycistronic. 4.mRNAs are monocistronic.
Differences in Gene Expression Between Prokaryotes and EukaryotesDifferences in Gene Expression Between Prokaryotes and Eukaryotes

19. Christmas tree-like" structures can be visualized during activeChristmas tree-like" structures can be visualized during active
transcription-Yeast strains conditionally expressingtranscription-Yeast strains conditionally expressing

20. The Central Dogma of LifeThe Central Dogma of Life