Protein Synthesis
Chapter 12.3 & 12.4
AKA
Molecular Genetics PART II
PROTEINS & PHENOTYPE
This is part of molecular genetics because…
• The code to manufacture proteins is in the DNA
• ONE GENE  ONE PROTEIN
• The presence or absence of a protein determines
phenotype
• The sequence of amino-acids determines a
protein’s structure
• The structure of a protein determines its function
EXAMPLES OF IMPORTANT PROTEINS
Always REMEMBER the factory
• Central Dogma
• FYI – “Dogma” is a principle or set of principles laid down by an authority
as incontrovertibly true.)
• Central Dogma of Biology
•DNA  mRNA  Protein
• ….proteins allow cells to function
• Genotype determines proteins form/fcn which determines phenotype
• T & T = Transcription and Translation
HOMEWORK!!! = 12.3 Read/Notes
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RNA is similar to DNA. 3 differences are:
1.
2.
3.
RNA contains the sugar ribose instead of deoxyribose.
RNA uses the nitrogen base Uracil in place of Thymine.
RNA is single-stranded while DNA is double-stranded.
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There are three main types of RNA that play a role
in protein synthesis.
1.
2.
3.
Messenger RNA (mRNA)
Ribosomal RNA (rRNA)
Transfer RNA (tRNA).
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DNA contains a code that is transcribed into another nucleic acid
called RNA (ribonucleic acid).
RNA is the photocopy of DNA that directs synthesis of proteins.
This is process is known as the Central Dogma of biology.
DNA is transcribed into a Messenger RNA (mRNA).
Messenger RNA carries information to the ribosomes.
Ribosomes (Ribosomal RNA - rRNA) and Transfer RNA (tRNA)
translate the code to make the proteins.
This is how genes are expressed as traits. = Molecular Genetics
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The job or role of mRNA is transcription.
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Transcription is the process of copying the DNA code.
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Again…this is the role of messenger RNA (mRNA).
Messenger RNA enters the nucleus, a small portion of the
DNA strand is transcribed. Then the messenger RNA leaves
the nucleus after copying down a part of the code to make
a protein.
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After the DNA is unwound in the nucleus, an enzyme comes
along to assist in base pairing, called RNA polymerase.
RNA polymerase assists mRNA in recording what information
is found on a portion of the DNA strand.
Messenger RNA transcribes the code in complementary base
pairs (similar to the way DNA bases are paired during replication)
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exception when the base pair Adenine is paired,
Adenine pairs with Uracil instead of Thymine. (AU)
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After the mRNA is transcribed, mRNA can leave the nucleus
through nuclear pores and enter into the cytoplasm to find
transfer RNA (tRNA) and ribosomal RNA (rRNA).
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After a mRNA finds a ribosome, the code is read and translated
by interpreters called transfer RNA (tRNA).
tRNA interprets the code on the mRNA by reading its bases in
groups of three called Codons.
Transfer RNA molecules each have their own Anticodon that
only matches with a specific codon.
Translation Animation. (3 min. + 5Q quiz)
Codon – mRNA or DNA
Anticodon - tRNA
1. codon recognition
2. peptide formation
3. translocation
4. termination (stop codon)
ANOTHER WAY TO THINK ABOUT IT…
1. INITIATION (start codon)
2. ELOGATION
-peptide formation
-translocation
3. TERMINATION (stop codon)
NARRATED ANIMATION: 3 min.
Ribosome
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The DNA code is
read as a three-base
code system.
Each codon matches
with a specific
anticodon and a
specific amino acid.
By joining multiple
amino acids together,
proteins can be
assembled.
• Only 20 amino acids.
Teacher’s Pet: Transcription and Translation
Teaches how to use the RNA Codon Chart
to find the amino acid
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•
•
•
Complete, detailed T&T Animation
Amoeba Sisters: Protein Synthesis
Crash Course: Transcription and Translation.
Teacher’s Pet: Transcription and Translation
• Teaches how to use the RNA Codon Chart to find the amino acid
• Mr. W – TNT Parody
TAG
UAG
5’
3’
5’
3’
3’
5’
• What molecule is 1?
What molecule is 2?
5’
3’
3’
5’
5’
3’
5’
3’
3’
5’
5’
3’
5’
3’
3’
5’
5’
3’
NORMAL DNA Replication MISMATCH REPAIR
• A mutation is a permanent alteration in the DNA
nucleotide sequence that makes up a gene of an
organism.
• Caused by mistakes when the DNA is copied
TYPES OF MUTATIONS….WHITE BOARD BIOLOGY (6 min)
Point Mutation
Frame-shift Mutation
Mis-sense Mutation
Non-sense Mutation
Point-mutation – Base Substitution
• A gene will be made up of a string of these codes rather like a
string of 3-letter words in a sentence. We'll use that as a simple
analogy. Take the sentence:
the big fox bit the dog but not the boy
• Suppose one letter got changed in this by accident. Suppose, for
example, the "d" in dog got replaced by a "p". The sentence
would now read:
the big fox bit the pog but not the boy
Double stranded…both bases replaced
Frame-shift mutation – Base Deletion
• A gene will be made up of a string of these codes rather like a
string of 3-letter words in a sentence. We'll use that as a simple
analogy. Take the sentence:
the big fox bit the dog but not the boy
• If you delete a single base:
the big fxb itt hed ogb utn ott heb oy
• This time the "o" in "fox" has been deleted. And again, because
we have to read the letters in groups of three, the rest of the
sentence becomes completely wrecked.
Frame-shift mutation – Base Addition
• A gene will be made up of a string of these codes rather like a
string of 3-letter words in a sentence. We'll use that as a simple
analogy. Take the sentence:
the big fox bit the dog but not the boy
• If you insert a single extra base:
• the big fro xbi tth edo gbu tno tth ebo y
• An extra "r" is inserted in "fox". If the sentence still has to be
read three letters at a time (as in DNA), everything from then on
becomes completely meaningless.
RESULT? –
Mis-sense or Non-sense?
1.
2.
RESULT? –
Mis-sense or Non-sense?
• Cystic fibrosis
30K People in USA
TEAM MISSY
• 1 minute video explaining mutation
Connection to Malaria- Evolution
• Sufferers from hemophilia lack a protein in the blood which
allows it to clot. That means that if someone with hemophilia cuts
themselves, the wound will just continue to bleed.
• There are all sorts of mutations which cause hemophilia. One
which is easy to understand is caused by changing a single base
at the beginning of a codon for arginine (CGA) somewhere in the
gene to give TGA. If you look back to the codon table, you will
find that TGA is a stop codon.
• All that will be produced is a useless fragment of the intended
protein.
CGA  TGA … What kind of mutation?
KNOWN METHODS OF GENE REGULATION
1. Histone blocking
2. X-chromosome inactivation
3. Transcription factors
4. Enhancers
5. Alternate gene splicing
6. miRNAs
7. RNA Breakdown
8. Protein Activation (timing)
9. Protein breakdown
What did your body use the nutrients
you consumed for?
HINT: Carbohydrates, Lipids, Proteins, Nucleic Acids
What is a codon?
Define and Give an example of one…
HINT: DNA/RNA “words”
What is a mutation?
Define and Give an example of one…
HINT: whoops!
What is #1?
What is #2?
#1 – Process?
#2 – Process?
HINT:
5’
3’
5’
3’
5’
• What molecule is 1?
What molecule is 2?
Instructions:
• 1. Pass out blank bingo cards
• A simple exercise to help • 2. Students should fill out
students learn how to use each of the blanks with an
amino acid from the codon
a codon table to
translate mRNA into its
chart.
associated amino acids. • 3. Teacher calls out 3 bases
(A, T, G, C)
• 4. Students find the amino
acid that is associated with
the codon and mark the
square (use bingo chips or
pennies or other
miscellaneous items)
• Reverse process to check
understanding
• Each Student Receives
their own 4 Amino Acid
Sequence.
• DNA Model must be built
correctly with the DNA
Nucleotides in the correct
order (see rubric)
• DUE 12/15/2016