Transcript Transcription - Kenmore Tonawanda UFSD

Protein Synthesis
DNA’s destiny!
Protein Review
• Long chains
(POLYPEPTIDES)
formed by 20 different
amino acids
• Protein shape is
determined by DNA
sequence!
SO HOW DO WE GO
FROM DNA TO
PROTEIN??
POLYPEPTIDE MADE
OF MANY AMINO ACIDS
What does DNA really do?
• The genes in DNA must code for something
right??? So what IS IT????
• The DNA alphabet (A, T, C, G) essentially
codes for amino acids
– Which are the building blocks for…….
PROTEINS!!!!!!!!!!
What does DNA do?? Con’t……
• The order of bases in DNA contains
a code for a SPECIFIC order of
amino acids
• The order of amino acids
determines the shape and function
of the protein
DNA to Protein overview
DNA
TAKES
PLACE IN
NUCLEUS
mRNA
Ribosome
“reads” mRNA
TAKES PLACE
IN
CYTOPLASM
tRNA brings proper AMINO ACIDS to ribosome as mRNA is read
Amino acids are linked together to make PROTEIN that gene coded for
DNA to Protein Overview:
The 2 phases
• PHASE 1: In the NUCLEUS
– Called TRANSCRIPTION
– “Transcribing” DNA to single strand of mRNA
– This creates a “readable” message for ribosomes
• PHASE 2: In the CYTOPLASM
– Called TRANSLATION
– Ribosomes “translate” the message found on the
mRNA strand into amino acids
– The amino acids are strung together to make the
protein the gene coded for
DNA to PROTEIN
http://www.you
tube.com/watc
h?v=983lhh20r
GY
RNA Basics
• RNA is single stranded
• Contains U (uracil) instead of T (thymine)
– So A binds with U in RNA
• Types of RNA:
– mRNA
• Messenger RNA
• Result of transcription
• Contains a message from DNA
– tRNA
• Transfer RNA
• Brings proper amino acid to ribosome during translation
Phase 1: Transcription- Making
mRNA
Occurs INSIDE THE NUCLEUS
1. DNA strands separate at the bases
2. Complimentary RNA bases take their places
along one of the DNA strands with the help of
enzymes
–
–
–
Remember…..RNA bases are A, C, G, and U
(uracil)
U instead of T!
This creates an mRNA strand
Let’s see this in action!
Phase 1: Transcription con’t…
Let’s practice making mRNA from a DNA strand!
DNA mRNA
Strands Strand
T
A
A
A
U
T
C
G
G
T
A
A
T
A
A
A
U
T
G
C
C
A
U
T
T
A
A
mRNA is constructed using
DNA
IS strand
UNZIPPED
ONE
of DNA. mRNA
pairs U with
A, instead of T.
mRNA leaves nucleus
and attaches to a
ribosome in the cytoplasm
Diagram of Transcription
Phase 2: Translation- Making a
Protein
Occurs in the CYTOPLASM at a
RIBOSOME
1. mRNA from transcription leaves the
nucleus
2. mRNA attaches to a ribosome
3. Ribosome “reads” the message in the
mRNA
•
•
Ribosomes can only read 3 bases at a
time!!!
3 mRNA bases is called a CODON.
Translation con’t….
4. Reading mRNA by ribosome signals a
tRNA to bring the correct amino acid
• A codon codes for 1 amino acid
(LOOK AT YOUR CODON SHEET)
• Ex. AUG codes for tRNA to bring
Methionine
5. tRNA drops off amino acid at the
ribosome
Translation con’t….
6. Ribosome “reads” the next codon to
signal for the next amino acid
7. Amino acids are connected by
BONDS as they are brought by
tRNA
8. The last codon read is a STOP
codon that means the protein is
complete!
Translation Diagram
Forming Polypeptide
Ribosome
mRNA
Close up of translation
Let’s practice Translation!
• The strand we made earlier
is:
• If 3 bases code for 1
amino acid, how many
amino acids are coded for
in our strand?
3 of course!
• Using your CODON
SHEET, translate the
mRNA codons into 3
amino acids
A
U
G
A
A
U
C
U
A
mRNA
Strand
Translation Example
A
U Ribosome
tRNA brings
Methionine
G
Peptide
Bond
A
A Ribosome
tRNA brings
Asparagine
U
C
U Ribosome
A
tRNA brings
Leucine
Let’s do the whole thing
together!
• DNA strand:
TACAAACATGGCTGATCGATT
• mRNA strand
AUG|UUU|GUA|CCG|ACU|AGC|UAA
• Amino Acids
MET-PHE-VAL-PRO-THR-SER-STOP
Protein Synthesis Overview