Download Translation - Crestwood Local Schools

PROTEIN
SYNTHESIS
Do these people represent DNA or RNA?
How do you know?
DNA
• DNA contains genes, sequences
of nucleotide bases
• These Genes code for
polypeptides (proteins)
• Proteins are used to build cells
and do much of the work inside
cells
Genes & Proteins
 Proteins are made of amino
acids linked together by
peptide bonds
 20 different amino acids exist
Amino Acid Structure
Polypeptides
• Amino acid chains
are called
polypeptides
Pathway to Making a Protein
DNA
mRNA
tRNA (ribosomes)
Protein
Protein Synthesis
 The production or synthesis of
polypeptide chains (proteins)
 Two phases:
 Transcription
 Translation
 mRNA must be processed
before it leaves the nucleus of
eukaryotic cells
The Genetic Code
• A codon designates an amino acid
• An amino acid may have more than
one codon
• There are 20 amino acids, but 64
possible codons
• Some codons tell the ribosome to
stop translating
Codons
• Sets of 3
Base Pairs
• Each codes
for an amino
acid
• Redundancy
• Start codon
AUG
Codons
• Sets of 3
Base Pairs
• Each codes
for an amino
acid
• Redundancy
• Start codon
AUG
Name the Amino Acids
•
•
•
•
•
GGG?
UCA?
CAU?
GCA?
AAA?
What does it mean to
translate?
To change from one form
into another
Big Picture overview of
transcription and translation:
Transcription: Making an
RNA copy of the DNA
Translation: Making a
protein from the RNA
copy
How do we refine the
central dogma to include
transcription and
translation?
Why not just use the
DNA to make a protein?
So what is the biological
understanding of TRANSLATION?
the process of matching amino acids to
corresponding sets of three bases (codons) and
linking them into a protein.
What are codons?
AUGCCGUUAUUA
Each series of corresponding three bases
What are amino acids?
20 different small molecules that link together in
long chains to form proteins.
Often referred to as the "building blocks" of
proteins.
How does TRANSLATION work?
1. You have a your resulting RNA strand
from transcription
UGACUUGGACUA
2. Each codon is translated into a specific
AMINO ACID
a. The tRNA reads the code on the mRNA
and brings the right amino acid
b. The ribosome links the amino acids into a
chain to make a protein
.
Three Types of RNA
• Messenger RNA (mRNA) copies DNA’s
code & carries the genetic information
to the ribosomes
• Ribosomal RNA (rRNA), along with
protein, makes up the ribosomes
• Transfer RNA (tRNA) transfers amino
acids to the ribosomes where proteins
are synthesized
Messenger RNA (mRNA)
• Long chain of nucleotides
that carries the information
for a specific protein
• Made in the Nucleus (500 –
1000 nucleotides long)
• Contains the Nitrogen Bases
A, G, C, U ( no T )
• Copies DNA & leaves
through nuclear pores
Transfer RNA (tRNA)
• Clover-leaf shape
• Each tRNA carries a
specific amino acid
• Single stranded molecule
with attachment site at
one end for an amino acid
• Opposite end has three nucleotide
bases called the anticodon
– Anticodon: three tRNA nucleotides
that will hydrogen bond with the
mRNA codon
Codons and Anticodons
• The 3 bases of an anticodon
are complementary to the 3
bases of a codon
• Example:
– Codon ACU
– Anticodon UGA
U
G
A
A
C
U
Transfer RNA
amino acid
attachment site
U A C
anticodon
Ribosomal RNA (rRNA)
• rRNA is a single strand
100 to 3000 nucleotides
long
• Globular in shape
• Made inside the nucleus
of a cell
• Associates with proteins
to form ribosomes
• Site of protein
Synthesis
Ribosomes
• Made of a large
and small subunit
• Composed of
rRNA (40%) and
proteins (60%)
• Have two sites
for tRNA
attachment:
– P and A
Amino acid
•Messenger RNA
•Carries the message from the DNA
to the ribosome to build a protein
•Transfer RNA
Ribosome
•Transfers amino acids
onto the protein as it is
being made
Transfer RNA
(tRNA)
•Ribosomal RNA
•Part of the ribosome
Codon
Ribosomal RNA
(rRNA)
Messenger RNA (mRNA)
Translation
• Translation is the process of
decoding the mRNA into a
polypeptide chain
• Ribosomes read mRNA three
bases or 1 codon at a time and
construct the proteins
Key things to remember
•
A protein always begins with the same
START codon: RNA codon AUG and the
amino acid methionine (met).
•
A protein is finished when it reaches a
STOP codon: RNA codons: UAA, UGA,
UAG
•
Don’t try to memorize the code. It will
be given to you. Just learn the start
codon.
Site of Translation: Ribosomes
Large
subunit
P
Site
A
Site
mRNA
A U G
Small subunit
C U A C U U C G
Step 1- Initiation
• mRNA transcript start
codon AUG attaches to
the small ribosomal
subunit
• Small subunit attaches
to large ribosomal
subunit
mRNA transcript
Initiation
aa1
aa2
2-tRNA
1-tRNA
anticodon
hydrogen
bonds
U A C
A U G
codon
G A U
C U A C U U C G A
mRNA
Step 2 - Elongation
• As ribosome moves, two tRNA with their
amino acids move into site A and P of the
ribosome
• Peptide bonds link the amino acids together
Elongation
peptide bond
aa1
1-tRNA
anticodon
hydrogen
bonds
U A C
A U G
codon
aa2
2-tRNA
G A U
C U A C U U C G A
mRNA
aa1
peptide bond
aa3
aa2
1-tRNA
3-tRNA
U A C
(leaves)
2-tRNA
A U G
G A A
G A U
C U A C U U C G A
mRNA
Ribosomes move over one codon
aa1
peptide bonds
aa2
2-tRNA
A U G
aa3
3-tRNA
G A U G A A
C U A C U U C G A A C U
mRNA
aa1
peptide bonds
aa4
aa2
aa3
2-tRNA
4-tRNA
G A U
(leaves)
3-tRNA
A U G
G C U
G A A
C U A C U U C G A A C U
mRNA
Ribosomes move over one codon
aa1
peptide bonds
aa2
aa3
3-tRNA
aa4
4-tRNA
G A A G C U
G C U A C U U C G A A C U
mRNA
peptide bonds
aa1
aa5
aa2
aa3
aa4
5-tRNA
U G A
3-tRNA
G A A
4-tRNA
G C U
G C U A C U U C G A A C U
mRNA
Ribosomes move over one codon
aa4
aa5
Termination
aa199
aa3 primary
structure
aa2 of a protein
aa200
aa1
200-tRNA
A C U
mRNA
terminator
or stop
codon
C A U G U U U A G
37
End Product –The Protein!
• The end products of protein
synthesis is a primary structure
of a protein
• A sequence of amino acid
bonded together by peptide
bonds
aa2
aa3
aa4
aa5
aa199
38
aa1
aa200
NUCLEUS
1. mRNA is transcribed
in the nucleus.
mRNA
Phenylalanine
Methionine
tRNA
Lysine
2. mRNA enters cytoplasm
& attaches to ribosome
at the “start codon.”
3. tRNA with the correct anticodon brings in the next
amino acid in the sequence.
RIBOSOME
Start codon
mRNA
RIBOSOME
Growing
polypeptide chain
tRNA
4. The ribosome joins
the two amino acids
& releases the tRNA.
Lysine
tRNA
5. The ribosome moves
along the mRNA to bind
new tRNA molecules
and amino acids.
mRNA
6. The process continues until the
ribosome reaches a stop codon.
RIBOSOME
Direction
of
translation
Key things to remember
•
A protein always begins with the same
START codon: RNA codon AUG and the
amino acid methionine (met).
•
A protein is finished when it reaches a
STOP codon: RNA codons: UAA, UGA,
UAG
•
Don’t try to memorize the code. It will
be given to you. Just learn the start
codon.
Practice
Replication
DNA Strand:
ACTACGTTAGAACT
Complimentary Strand?
TGATGCAATCTTGA
Practice
Transcription
DNA:
ACTACGTTAGAACT
mRNA:
UGAUGCAAUCUUGA
Practice
(use your amino acid decoder)
Translation
mRNA:
UGA U GCAAUCUUGA
Amino acid sequence:
met – gln – ser - STOP