protein synthesis
DESCRIPTION
Protein SynthesisTRANSCRIPT
PROTEIN SYNTHESIS
CENTRAL DOGMA OF MOLECULAR BIOLOGY
DNA
RNA
Protein
transcription
translation
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…
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
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.
ANIMATION
• http://207.207.4.198/pub/flash/26/transmenu_s.swf
CLIK here to view an animation of the whole process of transcription!
TRANSLATIONDNA
M RNA
PROTEIN
transcription
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.
translationThe 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
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
GENETIC CODEEven though there are only 20 amino acids
that exist, there are actually 64 possible
tRNA molecules:
4 X 4 X 4 = 64 possible combinations
CODONCODON CODON G C U
1º NUCLEOTIDE
2º NUCLEOTIDE
3º NUCLEOTIDE
=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 to DNA?
Why can it be reffered to the DNA?
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 DEGENERATEAs 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)
TRANSLATIONLOADED tRNA
RIBOSOME
mRNA
COMPONENTS PRESENT IN THE PROCESS
anticodon
Aminoacid carried
codon
TRANSLATIONThe 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.
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)
TRANSLATION
A
2º AMINOACID: Glycine (only in this case) in site A.
PEPTIDIC BOND IS FORMED
TRANSLATION
STOP codon NO aminoacid is added. Its the END of the polypeptide!
Growing polypeptide
POLYSOMES
ANIMATION
• http://ncc.gmu.edu/dna/ANIMPROT.htm
CLIK here to view an animation of the whole process of translation!