Download DNA / RNA

DNA / RNA
5’
3’
mRNA
Types of RNA
rRNA
tRNA
• Transcription: transfer of information from
DNA to RNA in the nucleus
In the process of transcription DNA is used to make a
complimentary strand of RNA
o The WHOLE strand of DNA doesn’t get turned into RNA
at once
o Instead, as needed, small sections of DNA are
transcribed into RNA
• Sections are called???
GENES
o
Transcription:
If a gene is transcribed into mRNA it is
being “expressed”
Having the gene in your DNA is not
enough
It MUST be turned into RNA to do
anything
Genetic Code:
Every three bases of the mRNA is
called a Codon
Each codon represents an Amino Acid
The first codon of a gene is ALWAYS
AUG
5’
3’
A UGA GG
Genetic Code:
There are 64 possible three base
combinations of AUGC
• 1 is the start codon AUG
(methionine)
• 3 are stop codons and tell the cell
when the protein is done: UAA,
UAG, UGA
• The other 60 represent the other 19
amino acids.
Genetic Code:
AUG tells the cell to bring in the amino
acid Methionine
AGG tells the cell to bring in a different
amino acid, arginine
5’
3’
A UGA GG
Translation:
The mRNA formed in transcription is
taken to the ribosome where it serves
as the directions to form a sequence of
amino acids which form proteins.
- Ribosome is made out of protein and
rRNA
Translation:
Step 1: mRNA lines up in the ribosome
5’
A UGA GG
Translation:
Step 2: Enter tRNA
- tRNA is a twisted up piece of RNA
with an amino acid attached to one
end
V. Translation:
Step 2: Enter tRNA
Only bases we are interested in are
the 3 at the bottom
- These are called
the Anti-codon
Translation:
Step 2: Enter tRNA
There is a tRNA with a unique anticodon for each
Amino Acid
- The anti-codon
binds to its
complimentary
codon in the
mRNA
Translation:
Step 2: tRNA with anti-codon
complimentary to AUG enters Ribosome
with the first amino acid
AA
1
5’
Translation:
Step 3: Next tRNA enters and chain of
amino acids begins
AA2
AA1
5’
Translation:
Step 3: Next tRNA enters and chain of
amino acids begins
AA1
5’
AA2
Translation:
Step 3: Next tRNA enters and chain of
amino acids begins
AA1
5’
AA2
Translation:
Step 4: A covalent Bond forms between
AA1 and AA2
AA1
5’
AA2
Translation:
Step 5: Ribosome shifts, releases tRNA
1, opens up new codon on the mRNA
AA3
AA1
AA2
5’
3
Translation:
Step 5: Ribosome shifts, releases tRNA
1, opens up new codon on the mRNA
AA1
5’
AA2
AA3
3
Translation:
Step 5: Ribosome shifts, releases tRNA
1, opens up new codon on the mRNA
AA1
5’
AA2
AA3
3
Translation:
Step 5: Ribosome shifts, releases tRNA
1, opens up new codon on the mRNA
AA1
5’
AA2
AA3
3
Translation:
Step 6: Process continues until open
codon is one of the 3 STOPS.
AA1
AA2
AA3
5’
STOP
3’
VI. Translation:
Step 7: Completed Protein is released.
AA3
AA2
AA1
5’
STOP
3’
Transcription
Translation
(happens in the nucleus)
(happens at the ribosome)
Translate the mRNA an amino Acid sequence.
Useful links - Lew - Port's Biology Place