CENTRAL DOGMA OF
Before cell division the cell’s DNA
has to duplicate
While the cell is growing it needs
enzymes and extra proteins…
THE INFORMATION FOR PROTEIN
SYNTHESIS IS IN THE DNA IN THE
THE INFO FROM THE DNA IS
COPIED INTO m RNA, WHICH CAN
LEAVE THE NUCLEUS AND GET TO
THE RIBOSOMES IN THE
THE PROTEINS ARE MADE IN THE
CYTOPLASM IN THE RIBOSOMES
COPIED TO mRNA
TRANSCRIPTION: the process
RNA polymerase: enzyme
that initiates transcription by
binding to promoter at the 3'
end of DNA, unwinds and
RNA polymerase, binds
the RNA nucleotides
together to form the
bases of the
Only 1 strand of
DNA in a gene
DNA info is copied into to RNA code, which is still in the
“language” of nitrogenous bases, except that adenine on
the DNA pairs with uracil (in place of thymine) on the
RNA. HAPPENS IN NUCLEUS.
The RNA code is then translated to protein code, which
is a different “language.” (nitrogenous bases to
This process involves ribosomes and two kinds of RNA:
mRNA and tRNA. HAPPENS IN CYTOPLASM
INFORMATION IN THE mRNA
Codon: sequence of 3 nucleotides on
m-RNA that codes for one amino acid.
The GENETIC CODE states which codon
stands for which aminoacid.
Even though there are only 20 amino acids
that exist, there are actually 64 possible
4 X 4 X 4 = 64 possible combinations
G C U =Gly
GENETIC CODE (II)
The GENETIC CODE
can be reffered as
well to the DNA, as
in this case.
How can you tell this
GENETIC CODE reffers
Why can it be reffered to
CHARACTERISTICS OF THE
It can be reffered to DNA or RNA.
It is UNIVERSAL.
All living organisms share the same code.
We can “read” the DNA of a bacterium, a plant or a worm
using the same code!! PROOF FOR EVOLUTION!!!
It is DEGENERATE
As there are ONLY 20 aminoacids but 64 possible
Each aminoacid has MORE
than ONE codon!
There are codons that code for punctuation (START and STOP)
IN THE PROCESS
The newly made mRNA (transcription) leaves the nuceus and binds with the
ribosome in the cytoplasm.
ONE codon is exposed at site P and
another codon at site A
A tRNA with a complementary codon
in its anticodon site will bind with the
codon at site P, bringing an
in site P.
Even though every protein begins with the Methionine amino acid, not all
proteins will ultimately have methionine at one end. If the "start"
methionine is not needed, it is removed before the new protein goes to
work (either inside the cell or outside the cell, depending on the type of
Glycine (only in this case) in site A.
PEPTIDIC BOND IS FORMED
NO aminoacid is added. Its the
END of the polypeptide!