Transcript Protein Synthesis

By the end of this unit you will:
 know what transcription is
 know what translation is
 understand how proteins are made.
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DNA contains the genetic code which controls
the production of proteins
Proteins, as we have learned, do everything!
There are two important events which must
happen in order to make a protein;
transcription and translation
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Transcribing or copying the coded message of
DNA onto a single stranded nucleic acid called
mRNA
DNA’s code is contained in groups of 3
nitrogen bases called DNA triplets
One side of DNA is considered the coding side,
or template, and the other side is considered
the complimentary side.
Left side – coding side
Right side – complimentary strand
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To begin transcription, Helicase causes the
molecule to split or “unzip”.
This exposes the nitrogen bases of the coding
side
Free floating mRNA nucleotides attach to the
coding side of DNA
The whole mRNA strand is removed from the
coding side of DNA
The mRNA strand then moves out of the
nucleus and heads for a ribosome.
The DNA strand then can re-attach with the
complementary side of DNA
Transcription and the TATA's
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Each group of 3 nitrogen bases of mRNA
are called codons.
•Use the
code by
reading from
the center to
the outside
•Example:
AUG codes
for
Methionine
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GGG?
UCA?
CAU?
GCA?
AAA?
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Transcription is copying the DNA code onto a
mRNA molecule.
mRNA leaves the nucleus and moves to the
ribosome where the message is translated
AUG is called the “Initiation Codon” . It begins
the process and always codes for Methionine
“Termination Codons” indicate the end of the
process. UAG,UAA, and UGA are termination
codons and don’t code for any amino acids
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Assume the sequence of nitrogen bases below
represents the coding side of DNA.
 ACT CCC CGA TAC
Transcribe the DNA triplets into mRNA
codons
Draw the mRNA molecule that would be
produced during Transcription.
Translate the mRNA molecule into the amino
acids it represents. Use your codon wheel.
DNA contains the genetic code for the production of __________.
Each group of 3 nitrogen bases in DNA is called a __________.
The genetic code of _____ is trapped inside the nucleus because it is
____________ to fit through the pores in the nuclear envelope.
__________ is the process of copying the genetic code of _____ onto a single
strand of _____.
The single stranded _____ molecule falls on it’s side with it’s nitrogen bases
pointing _____ and moves out of the nucleus to find a __________.
Each group of 3 nitrogen bases in mRNA is called a __________.
AUG is a special codon that is called an ________________. It always codes
for the amino acid __________.
Check you codon wheel and identify the amino acids that the following
codons code for:
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GGC - __________
UUU - __________
CAU - __________
GUA - __________
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Another special codon found in mRNA stops the chain of
amino acids and indicates the protein is complete. These
codons are called ________________. There are only 3 of the
codons: _______; ________ and _______.
We are always going to assume that the coding side of DNA
will be the __________ side.
Opposite the coding side is called the __________ side.
Two enzymes play a role in transcription: ____________
unzips the DNA molecule and __________________ helps
attach the free-floating mRNA nucleotides to the coding side
of DNA.
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DNA contains the genetic code for the production of Protein.
Each group of 3 nitrogen bases in DNA is called a DNA triplet.
The genetic code of DNA is trapped inside the nucleus because it is too big
to fit through the pores in the nuclear envelope.
Transcription is the process of copying the genetic code of DNA onto a
single strand of mRNA.
The single stranded mRNA molecule falls on it’s side with it’s nitrogen
bases pointing up and moves out of the nucleus to find a ribosome.
Each group of 3 nitrogen bases in mRNA is called a codon.
AUG is a special codon that is called an Initiation codon. It always codes for
the amino acid Methionine.
Check you codon wheel and identify the amino acids that the following
codons code for:
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GGC - Glycine
UUU - Phenylalanine
CAU - Histidine
GUA - Valine
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Another special codon found in mRNA stops the chain of
amino acids and indicates the protein is complete. These
codons are called Termination codons. There are only 3 of the
codons: UGA; UAA and UAG.
We are always going to assume that the coding side of DNA
will be the left side.
Opposite the coding side is called the complimentary side.
Two enzymes play a role in transcription: Helicase unzips
the DNA molecule and RNA polymerase helps attach the
free-floating mRNA nucleotides to the coding side of DNA.
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The process where the message of mRNA is
translated into sequences of amino acids.
Translation happens on the surface of
ribosomes.
3 codons can fit on the ribosome at one time.
Remember tRNA?
 amino acid (specific
to tRNA)
 tRNA molecule
 nitrogen bases called
anticodons
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Each tRNA molecule with one specific
anticodon sequence can carry only one specific
amino acid.
If the anticodon of tRNA is complimentary to
the codon of mRNA the amino acid carried by
that tRNA is dropped off.
Protein Synthesis PH
Let’s go back to our mRNA molecule. Draw the
respective tRNA molecules that would be
involved in Translation.
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Translation
Translation 2
Translation 3
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Use your codon chart to complete the following
table:
Codon
AUG
(initiation
codon)
UCC
AAA
CGU
Amino Acid
Anticodon DNA
triplet
←
←
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Gene A
Gene B
Exons – translatable segments of a
chromosome
Introns – segments of DNA that do NOT
code for proteins
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Nonsense DNA
AUG – intiation codon
Codes for methionine
UAA, UAG, and UGA are all
termination codons
“A” Site
• Arrival Site
• First tRNA arrives
“P” Site
“P”
Site
•Peptidyl Site
•Amino Acids bond together
“E” Site
•Exit site
•Naked tRNA goes to find
another amino acid
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Another look at Protein Synthesis
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Assume the strand of DNA nucleotides below
represents the coding side (The Boyfriend!)
 ACT CCA CGA TAC
Draw the mRNA molecule that would be
transcribed.(Value: 4)
Draw the three tRNA molecules that would be
complimentary to the mRNA molecule you
created. Make sure the appropriate amino acid
and anti-codon are positioned on the tRNA
drawings. (Value: 3)
Using you amino acid chart, draw the
polypeptide that would be created. (Value:3)
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Point Mutation: A change in one nitrogen base
in DNA.
EX: DNA
AAA TCT CGA
mRNA
UUU AGA GCU
Amino Acids
Phen-Arg-Ala
Point Mutation
DNA
AAA TGT CGA
mRNA
UUU ACA GCU
Amino Acids
Phen-Thre- Ala
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DNA
mRNA
A.A.
DNA
mRNA
A.A.
AAA TCT CGA
UUU AGA GCU
Phen-Arg-Ala
AAA TCC CGA
UUU AGG GCU
Phen – Arg - Ala
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- Mutation that deletes or adds a nitrogen base
pair.
- The result impacts the rest of the amino acids
in the chain
DNA
AAA TCT CGA
mRNA
UUU AGA GCU
A.A.
Phen – Arg- Ala
(Deletion)
AAA TCT CG_
mRNA
A.A.