protein synthesis trancription and translations

1. PROTEIN SYNTHESIS

2. CENTRAL DOGMA OF
MOLECULAR BIOLOGY
DNA
RNA
Protein
transcription
translation

3. GROWING CELL
Before cell division the cell’s
DNA has to duplicate
(DNA REPLICATION)
While the cell is growing it needs
enzymes and extra proteins…

4. TRANSCRIPTION
THE PROTEINS ARE MADE IN
THE CYTOPLASM IN THE
RIBOSOMES
THE INFO FROM THE DNA IS
COPIED INTO m RNA, WHICH
CAN LEAVE THE NUCLEUS AND
GET TO THE RIBOSOMES IN THE
CYTOPLASM.
THE INFORMATION FOR
PROTEIN SYNTHESIS IS IN THE
DNA IN THE NUCLEUS.
DNA INFO COPIED TO
mRNA

5. TRANSCRIPTION: the
process
Only 1 strand of
DNA in a gene
gets transcribed:
RNA polymerase: enzyme
that initiates transcription
by binding to promoter at
the 3' end of DNA,
unwinds and unzips it.
RNA activated
nucleotides
pair with the
complementary
bases of the
DNA strand
RNA polymerase, binds
the RNA nucleotides
together to form the
mRNA poynucleotide.

6. ANIMATION
• http://207.207.4.198/pub/flash/26/transmenu_s.swf
CLIK here to view an animation of the whole process of transcription!

7. TRANSLATION
DNA
M RNA
PROTEI
N
transcriptio
n
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.
translation
The RNA code is then translated to protein code,
which is a different “language.” (nitrogenous bases to
aminoacids.
This process involves ribosomes and two kinds of
RNA: mRNA and tRNA. HAPPENS IN CYTOPLASM

8. 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.
1 aminoacid
1 aminoacid

9. GENETIC CODE
Even though there are only 20 amino acids
that exist, there are actually 64 possible
tRNA molecules:
4 X 4 X 4 = 64 possible combinations
CODON
CODON CODON G C U
1º NUCLEOTIDE
2º NUCLEOTIDE
3º NUCLEOTIDE
=Gly

10. 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 to DNA?
Why can it be reffered to
the DNA?

11. CHARACTERISTICS OF
THE GENETIC CODE
 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
codons Each aminoacid has MORE
than ONE codon!
 There are codons that code for punctuation (START and STOP)

12. TRANSLATION LOADED tRNA
RIBOSOME
mRNA
COMPONENTS
PRESENT IN THE
PROCESS
anticodon
Aminoaci
d carried
codon

13. TRANSLATION
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
aminoacid.
1º AMINOACID:
Methionine (AUG)
in site P.

14. TRANSLATION
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
protein synthesized)

15. TRANSLATION
A
2º AMINOACID:
Glycine (only in this case) in site A.
PEPTIDIC BOND IS
FORMED

16. TRANSLATION
STOP codon NO aminoacid is added. Its
the END of the polypeptide!
Growing polypeptide

17. POLYSOMES

18. ANIMATION
• http://ncc.gmu.edu/dna/ANIMPROT.htm
CLIK here to view an animation of the whole process of translation!