Download File - Down the Rabbit Hole

Genes to Proteins
Transcription
and
Translation
DNA  RNA  Protein
• DNA contains genes
which provide the
information necessary
to make proteins
DNA
Transcription
• Different versions of
the same gene result in
different versions or
amounts of a protein,
and the differences in
the protein result in
different characteristics
Nuclear
membrane
Pre-mRNA
RNA Processing
mRNA
Ribosome
Translation
Protein
Don’t let this happen to you!!
RNA
How does RNA (ribonucleic acid)
differ from DNA (deoxyribonucleic acid)?
1.
2.
RNA has a sugar ribose
DNA has a sugar
deoxyribose
1.
2.
RNA contains uracil (U)
DNA has thymine (T)
1.
RNA molecule is singlestranded
DNA is double-stranded
2.
Transcription
• The process that copies the message in a gene into a
messenger RNA (mRNA) molecule that will provide the
instructions for making a protein molecule
• Started and controlled by an enzyme called RNA polymerase.
– RNA polymerase binds to the DNA at a special point (start signal)
– RNA polymerase unwinds and separates the two DNA strands
– RNA polymerase adds and links complementary RNA nucleotides as it
“reads” the gene until it reaches a “stop” signal
RNA
polymerase
DNA
mRNA
Transcription
Products of Transcription
1 Ribosomal RNA (rRNA) – Carrier molecule on
ribosomes – holds the tRNA and mRNA in
place
2 Transfer RNA (tRNA) - The molecule that
physically couples nucleic acid codons with
specific amino acids
3 Messenger RNA (mRNA) - The messenger that
carries information from genes on DNA to the
protein manufacturing ribosomes
Translation
The process that makes proteins. The sequence of nucleotides in
an mRNA molecule specifies the sequence of amino acids in a
protein.
This is a molecule of messenger RNA. It was
made in the nucleus by transcription from a DNA
molecule.
Codon= series of three nucleotides
A U G G G C U U AAA G C A G U G C A C G U U
mRNA molecule
Messenger RNA (mRNA)
start
codon
mRNA
Each codon translates into one of twenty
amino acids or is a stop or start signal
A U G G G C U C C A U C G G C G C A U A A
codon 1
protein methionine
codon 2
codon 3
glycine
serine
codon 4
isoleucine
codon 5
codon 6
glycine
alanine
codon 7
stop
codon
Primary structure of a protein
aa1
aa2
aa3
peptide bonds
aa4
aa5
aa6
The Genetic Code
UUU
UUC
UUA
UUG
CUU
CUC
CUA
CUG
AUU
AUC
AUA
AUG
GUU
GUC
GUA
GUG
Phenylalanine
Leucine
Leucine
Isoleucine
Methionine
Valine
UCU
UCC
UCA
UCG
CCU
CCC
CCA
CCG
ACU
ACC
ACA
ACG
GCU
GCC
GCA
GCG
Serine
Proline
Threonine
Alanine
UAU
UAC
UAA
UAG
CAU
CAC
CAA
CAG
AAU
AAC
AAA
AAG
GAU
GAC
GAA
GAG
Tyrosine
Stop
Histidine
Glutamine
Asparagine
Lysine
Asparagine
Glutamic
Acid
UGU
UGC
UGA
UGG
CGU
CGC
CGA
CGG
AGU
AGC
AGA
AGG
GGU
GGC
GGA
GGG
Cysteine
Stop
Tryptophan
Arginine
Serine
Arginine
Glycine
Note that 3rd Base Position is Variable
Eukaryotic Cell Protein Synthesis
Protein Synthesis occurs on Ribosomes
Protein Synthesis occurs on Ribosomes
A ribosome on the rough
endoplasmic reticulum attaches to
the mRNA molecule.
ribosome
AUGGGCUUAAAG CAGUGCACGUU
Along comes a Transfer RNA Molecule…
amino acid
attachment site
methionine
U A C
anticodon
amino acid
Amino acid
tRNA molecule
The tRNA brings an amino acid to the
first three bases (codon) on the
mRNA.
anticodon
The three unpaired bases
(anticodon) on the tRNA link up
with the codon.
UAC
AUGGGCUUAAAG CAGUGCACGUU
Another tRNA molecule comes into
place, bringing a second amino acid.
Its anticodon links up with the
second codon on the mRNA.
UAC
AUGGGCUUAAAG CAGUGCACGUU
Peptide
bond
A peptide bond forms between the
two amino acids.
AUGGGCUUAAAG CAGUGCACGUU
The first tRNA molecule releases its
amino acid and moves off into the
cytoplasm.
AUGGGCUUAAAG CAGUGCACGUU
The ribosome moves along the mRNA
to the next codon.
AUGGGCUUAAAG CAGUGCACGUU
Another tRNA molecule
brings the next amino acid
into place.
AUGGGCUUAAAG CAGUGCACGUU
A peptide bond joins the
second and third amino acids to
form a polypeptide chain.
AUGGGCUUAAAG CAGUGCACGUU
• The process continues.
• The polypeptide chain
gets longer.
• This continues until a
termination (stop)
codon is reached.
• The polypeptide is then
complete.
AUGGGCUUAAAG CAGUGCACGUU
There is a tunnel through the large subunit of the ribosome
that allows the growing polypeptide chain to pass out of the
ribosome
• Termination of
translation is triggered
by stop codons
• A release factor enters
the A site and triggers
hydrolysis of the
peptidyl-tRNA bond
leading to the release
of the protein.
Release of the protein
causes the disassociation
of the ribosome into its
constituent subunits.
Transcription And Translation
In Prokaryotes
5’
3’
3’
5’
RNA
Pol.
Ribosome
mRNA
5’
Ribosome
Everything happens
in the nucleus
Eukaryotic Transcription
Cytoplasm
DNA
Transcription
RNA
RNA
Processing
mRNA G
G
AAAAAA
Nucleus
Export
AAAAAA
Eukaryotic
Translation
Transcription/Translation Quiz
What is transcription?
Production of RNA molecules by copying part of DNA into a
complementary sequence of RNA
Why is transcription necessary?
Transcription makes messenger RNA (mRNA) to carry the
code for proteins out of the nucleus to the ribosomes in
the cytoplasm.
Describe transcription.
RNA polymerase binds to DNA, separates the strands,
then uses one strand as a template to assemble mRNA.
It uses the nucleotide bases except it replaces Thymine
with Uracil
Transcription/Translation Quiz
What is translation?
The genetic message encoded in RNA is used to
create a polypeptide with a specific amino acid
sequence
Describe translation.
The cell uses information from mRNA and tRNA
to produce proteins.
Why is translation necessary?
Translation assures that the right amino acids are
joined together by peptides to form the correct protein.
What are the main differences between DNA
and RNA?
DNA has deoxyribose, RNA has ribose; DNA has 2 strands,
RNA has one strand; DNA has thymine, RNA has uracil.