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 INFORMATION FOR PROTEIN
SYNTHESIS IS IN THE DNA IN THE
NUCLEUS.
THE INFO FROM THE DNA IS
COPIED INTO m RNA, WHICH CAN
LEAVE THE NUCLEUS AND GET TO
THE RIBOSOMES IN THE
CYTOPLASM.
THE PROTEINS ARE MADE IN THE
CYTOPLASM IN THE RIBOSOMES
DNA INFO
COPIED TO mRNA
5. TRANSCRIPTION: the process
RNA polymerase: enzyme
that initiates transcription by
binding to promoter at the 3'
end of DNA, unwinds and
unzips it.
RNA polymerase, binds
the RNA nucleotides
together to form the
mRNA poynucleotide.
RNA activated
nucleotides pair
with the
complementary
bases of the
DNA strand
Only 1 strand of
DNA in a gene
gets transcribed:
6. TRANSLATION
DNA
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.
M RNA
translation
PROTEIN
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
7. 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
8. 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
1º NUCLEOTIDE
CODON CODON
CODON
3º NUCLEOTIDE
G C U =Gly
2º NUCLEOTIDE
9. 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?
10. 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
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.
13. 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)
