Download 3.1 Class Notes Powerpoint

Unit 3.1 – Protein Synthesis
DAY 1
Journal Questions
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A question given to you every few
days
To be checked on Tuesdays during
Eagle time
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Mrs. Nedrow and Mrs. Mahan’s class go
to other Bio teacher
Turn all 6 in with test
Receive 6 extra credit points (1/q)
Warm Up
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INDIVIDUALLY:
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Create a thinking map to compare and
contrast DNA to RNA.
Where in the cell is it?
 What is it made of?
 Nitrogen Bases?
 Types
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Warm Up
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In small groups:
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Compare your thinking maps
Make changes to yours if you need to
RNA vs. DNA
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DNA
Double stranded
Deoxyribose sugar
Bases: C,G A,T
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RNA
Single stranded
Ribose sugar
Bases: C,G,A,U
Both contain a sugar, phosphate, and base.
Protein Structure
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Made up of amino acids
Polypeptide- string of amino acids
20 amino acids are arranged in
different orders to make a variety of
proteins
Assembled on a Ribosome
Questions to be answered today
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How do we get from the base
sequences found in DNA to a bunch
of amino acids?
How do we get from a bunch of
amino acids to proteins?
Replication
•DNA double helix unwinds
•DNA now single-stranded
•New DNA strand forms using
complementary base pairing (A-T, C-G)
•Used to prepare DNA for cell division
•Whole genome copied/replicated
DNA makes new DNA
Transcription and Translation: An
Overview (aka the Central Dogma)
DNA
Transcription
RNA
Translation
Protein
Transcription and Translation
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Cells are governed by a cellular chain of
command
We call this the “Central Dogma”
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Transcription
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DNA RNA protein traits
Is the synthesis of RNA under the direction of DNA
Produces messenger RNA (mRNA)
Translation
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Is the actual synthesis of a polypeptide, which occurs
under the direction of mRNA
Occurs on ribosomes
We’ll start discussing this process tomorrow.
Closing
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Write a short paragraph comparing
DNA to RNA - types, locations,
structure, etc.
COMPLETE SENTENCES!
DAY 2
Warm Up
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What type of RNA copies DNA?
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mRNA
What is this process called?
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Transcription
Transcription
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RNA forms base
pairs with DNA
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C-G
A-U (NOT T)
Primary transcriptlength of RNA that
results from the
process of
transcription
TRANSCRIPTION
ACGATACCCTGACGAGCGTTAGCTATCG
UGCUAUGGGACU
Major players in transcription
Messenger RNA

mRNA- type of
RNA that
encodes
information for
the synthesis of
proteins and
carries it to a
ribosome from
the nucleus
Major players in transcription
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RNA polymerase
2 functions:
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Unwind DNA
sequence
strings together
the chain of RNA
nucleotides
Does what both Helicase and DNA Polymerase did in DNA Replication
mRNA Processing
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Primary transcript
is not mature
mRNA
DNA sequence has
coding regions
(exons)
and non-coding
regions (introns)
Introns must be
removed before
primary transcript
is useful mRNA and
can leave nucleus
Let’s Practice!
Closing
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Write a “journal response” using the
Transcription vs. Translation
Handout as a guide…ONLY FILL IN
TRANSCRIPTION:
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Purpose
Process
Location in cell
End product
DAY 3
Warm Up
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Separate this DNA sequence into codons
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Transcribe this sequence & Splice out UAA
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ATTGCGATGTCGGCTGACCCC
ATT GCG ATG TCG GCT GAC CCC
UAA CGC UAC AGC CGA CUG GGG
UAA CGC UAV AGC CGA CUG GGG
What is this process called and why is it
important?

Gene splicing, to control gene expression
Transcription is done…what now?
Now we have mature mRNA
transcribed from the cell’s DNA. It
is leaving the nucleus through a
nuclear pore. Once in the
cytoplasm, it finds a ribosome so
that translation can begin.
We know how mRNA is made, but
how do we “read” the code?
Translation
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Second stage of protein production
Translation
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Translation is the RNA-directed
synthesis of a polypeptide
Translation involves:
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mRNA
Ribosomes - Ribosomal RNA
Transfer RNA
Genetic coding - codons
Step 1
Translation from mRNA to
Protein
• As translation begins, one end of mRNA strand
coming from the nucleus attaches to a ribosome.
mRNA strand
Ribosome
Reading the DNA code
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Every 3 DNA bases pairs with 3
mRNA bases
Every group of 3 mRNA bases
encodes a single amino acid
Codon- coding triplet of mRNA
bases
How many bases code for each
amino acid?
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3 bases = 1 codon
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1 codon = 1 amino acid
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3 bases = 1 amino acid
Step 2
Translation from mRNA to
Protein
• tRNAs bring amino acids to the ribosomes.
mRNA
Coming from
Nucleus
RIBOSOME
Amino
acid
Each tRNA only carries
one amino acid.
Transfer RNA
Bound to one amino
acid on one end
Anticodon on the
other end that
complements the
mRNA codon
• There are also three nucleotides on the bottom of the
tRNA called an anti-codon.
• Anti-codons complementary base pair with the codons
on mRNA.
(this is to make sure they are bringing the correct amino acidIf the anti-codon doesn’t base pair with the codon, then the
wrong amino acid was brought)
Anti-codon
• AUG is the first codon on the mRNA strand.
• This signals the ribosome to START making a protein
Methionine
• A tRNA with anticodon UAC comes and binds with this
codon and drops off it’s amino acid “Methionine”.
Step 3
• After the first tRNA binds with its codon, the
mRNA slides down so that the ribosome can read the
next codon.
Step 4
• A new tRNA molecule carrying an amino acid pairs
with the second mRNA codon.
Alanine
Step 5 • The amino acids then bond together.
• Once the first tRNA lets go of it’s amino acid, it is
released from the ribosome.
Methionine
Alanine
bond
• A chain of amino acids is formed until the
stop codon is reached on the mRNA strand.
The end result
is a protein
Stop
codon
Transcription vs. Translation Review
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Transcription
Process by which
genetic
information
encoded in DNA is
copied onto
messenger RNA
Occurs in the
nucleus
DNA
mRNA
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Translation
Process by which
information
encoded in mRNA
is used to
assemble a protein
at a ribosome
Occurs on a
Ribosome
mRNA
protein
PRACTICE!!!
Closing
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Write a “journal response” using the
Transcription vs. Translation
Handout as a guide…FILL IN
TRANSCRIPTION & TRANSLATION:
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Purpose
Process
Location in cell
End product
DAY 4
Warm Up
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Translate the following mRNA
strand into an amino acid strand
using the codon chart.
AUGCACUGUCCUUUCGCUGAC
The Genetic Code
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Genetic information is encoded as a sequence of nonoverlapping
base triplets, or codons
So now we get to the codon table!
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Locate the first
letter of your
codon using the
left side of the
table.
Ex. AUG
Look for the A
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Now move to the
second letter of
your codon which is
‘U’
Look across the top
of the table Find the
letter ‘U’ and follow
it down until it
intersects with the
letter ‘A’ from the
left side(1st letter).
You should see four
amino acids
(isoleucine,
isoleucine,
isoleucine, and
(start) methionine.
Codon:
AUG
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Down to the last
letter of the codon!
Look to the right
hand side for the
third letter. Find
the letter ‘G’ which
will intersect with
the box that had the
four choices.
Trace from the ‘G’ on
the left over to the
left and you should
land on …..
Methionine (start)
Yes you did it!!!
Now try another
codon
Codon:
AUG
Try the codon CAC
Did you get the
amino acid
‘histidine’?
What do these codons have to do
with proteins?
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Each codon
represents an amino
acid that will
eventually form a
protein that is used
within a cell.
Proteins are made
up of hundreds of
amino acids in a
specific sequence.
When they get “out
of order’ a mutation
occurs.
Long string
of amino
acids will
form
ACGATACCCTGACGAGCGTTAGCTATCG
UGCUAUGGGACUGCU
Let’s Practice…
DAY 5
Warm Up
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What is a mutation?
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Any changes that take place in DNA
Explain how a mutation can be a
benefit to an organism.
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The classic example of evolutionary change
in humans is the hemoglobin mutation that
makes red blood cells take on a curved,
sickle-like shape. With one copy, it resists
malaria, but with two copies, it causes the
illness of sickle-cell anemia.
Mutations
• Any change in DNA sequence is called a mutation.
• Mutations can be caused by errors during replication,
transcription, translation, or cellular division.
Types of Mutations you need to
know:
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Point Mutations
Frameshift Mutations
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Insertion
Deletion
Some mutations are inherited from
parents
• Mutations on sex cells (gametes) - passed on to
offspring.
• If a sperm or egg cell has a mutation and is fertilized,
the altered gene would become part of the genetic
makeup of the offspring. Every cell in that person
would contain the mutation.
• Sometimes a mutation can have no effect at all.
For instance, if a codon sequence was suppose to be
AUU
Why would it have no effect on the person if a mutation
caused the codon sequence to be
AUC
Some mutations occur
“randomly” in BODY CELLS
(any cell that is not a sex cell)
• What happens if powerful radiation hits the DNA of a
body cell, such as in skin, muscle, or bone?
Will that affect this person’s
offspring?
• If a body cell’s DNA is changed, this mutation would
not be passed on to offspring.
Types of Mutations
• A point mutation is a change in a single base pair in
DNA.
THE DOG BIT THE CAT.
THE DOG BIT THE CAR.
• Does this one letter change the meaning of the entire
sentence?
• Result: A change in a single nitrogenous base can
change the structure of a protein causing it to not
function properly.
Because one base was changed from a G to an A, it caused
the wrong amino acid to be put in the protein.
mRNA
Normal
Protein
Stop
Replace G with A
mRNA
Point
mutation Protein
Stop
It is called a point mutation, because it happens at
one point.
Types of Mutations
• A mutation in which a single base is added or
deleted from DNA is called a frameshift
mutation because all the codons shift from one
base.
• Also may be called: deletion mutation or
insertion mutation
Deletion of U
Types of Mutations
Result:
• Instead of just one amino acid being wrong, this
changes ALL the amino acids after the mutation.
• This causes much bigger problems than a point
mutation.
Deletion of U
Causes of Mutations
• Many mutations are caused by factors in the
environment, such as radiation, chemicals, and even
high temperatures.
• Any external agent that can cause a change in DNA is
called a mutagen.
Repairing DNA
• Enzymes proofread the DNA and replace incorrect
nucleotides with correct nucleotides.
• These repair mechanisms work extremely
well, but they are not perfect.
• The greater the exposure to a mutagen (such as UV
light), the more likely that a mistake will not be
corrected.
Cowabunga!!!