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Protein Synthesis
From DNA to protein
And viruses
BIG PICTURE
• Processing of Gene Information Prokaryotes versus Eukaryotes
• Transcription and
Translation
Beadle and Tatum
George Beadle and Edward
Tatum during the late 1930s and
early 1940s
• Using Neurospora crassa
bread mold determined "one
gene one enzyme hypothesis"
•has since been
modified to "one gene
one polypeptide"
Protein Synthesis Overview
Learn these Terms
• Transcription = DNA → mRNA
• Translation = mRNA → protein
Three Bases Lingo
• DNA
Triplet
ATC
• mRNA
Codon
UAG
Anti-codon
AUC
tRNA
Three Bases Lingo
• DNA original template
• mRNA codes from DNA, takes to
cytoplasm
tRNA brings amino acid to
ribosomes
rRNA structure of ribosome
Transcription
• DNA never leaves the nucleus
• It codes to mRNA to take the
message outside the nucleus
• What do you see?
• Transcription Animation (HOT!!)
Protein
Synthesis
Animation
TeacherTube
Videos –Protein
Synthesis (good
and to the point)
TeacherTube
Videos - DNA to
Protein
Introns and Exons
• Primary mRNA = exons +
introns
• INTRONS (noncoding region
of mRNA) are discarded
• The coding regions, spliced
together RNA are called EXONS.
= Mature
mRNA
SPLICING ANIMATION
• Spicing Animation from NobelPrize.org
Click on: Schematic animation
of mutually exclusive exons»
• Before the mRNA leaves the
nucleus, the introns are removed,
and the exons are spliced together.
• How Spliceosomes Process RNA
Intron and Exon Summary
TRANSLATION
• mRNA (genetic language)
needs to be translated into
protein language
• VCAC: Molecular
Processes: Translation: The
Movie
TRANSLATION
• Coding from mRNA to
making protein
• Animations (click here for
translation animation)
• Transcribe and Translate a
Gene (good activity)
The mRNA travels out of the nucleus
through nuclear pores to a ribosome in
the cytoplasm
The
mRNA
binds to a
ribosome
Ribosome
translates
codons (use
chart)
Translation
•Ribosome “reads”
each codon (3 bases)
on the mRNA.
• The mRNA “chart”
is consulted and the
correct amino acid is
determined.
•What amino acids
are being requested?
ANSWER
AGC =cysteine
UGA =STOP
CCU=proline
AGC =serine
GGA=glycine
CAA=glutamine
tRNA
• transports amino acids
to ribosomes
• There is a specific
amino acid for
each tRNA
Job of tRNA
• Complements the codon of mRNA
and picks up the appropriate amino
ANIMATION:
acid
Animation of Translation
•A tRNA with
the anticodon
complementary
to the codon is
sent to pick up
the requested
amino acid and
bring it to the
ribosome.
tRNA’s hang out in the cytoplasm. Think of them as
trucks that transport amino acids from where they
float around in the cytoplasm, to the ribosome.
Think of the anticodon as the license plate on the
tRNAthat matches the mRNA codon.
APE slots on the ribosome
• The ribosome attaches to the mRNA and
provides a slot (A) for the tRNA to slide
into so it can match the mRNA.
Note the P and A site
• Protein Synthesis: Translation
• A site – Amino acid is
dropped off
• P site – Polypeptide
builds
• E site-polypeptide exits
There are 20 Amino Acids
• These 20
are shared
by all living
organisms
Notice AUG codon means “start”
building a new protein. UAA,
UAG, UGA mean “stop’ building the
protein.
All mRNA’s start with AUG, so all
DNA genes start with______?
Answer
•Methionine
Nice Animations of Protein
Synthesis
• Shows Nucleus to Protein
• ☺Protein Synthesis
Animation
• Protein Synthesis Learning
Activity
- Flash Player Installation
• THINK:
• What would happen if something
caused the base sequence to
change?
• What sorts of things could cause this?
• Could the base changes be repaired?
• Would those changes be passed on
to the individual’s offspring?
Thalidomide baby…
MUTATION:
A change in the base sequence of a gene
resulting in a different base sequence and
thus different amino acid sequence.
What causes mutations? MUTAGENS
Examples of mutagens?
GOOD OR BAD?
Mutagen =any source of
mutation is a physical or
chemical agent
–EX: X-rays
–UV light
–cigarette components
–Hazardous chemicals
Mutation Lingo
• Mutation = any change in the genetic
material (nucleotide sequence of
DNA)
Gene (point)mutations
SUBSTITUTION – Replace one base for
another. Minimal effect
ADDITION – Adding a base
DELETION – removing a base
•Frameshift mutations =change every
amino acid that follows the point of
mutation
Chromosome Mutations
Translocation • Inversion
• has
moved
one segment
of a
chromosome
to a different
chromosome
• Segment of a
same
chromosome is
turned end to
end
Frameshift
• Animation Quiz 5 - Addition and Deletion
Mutations
Translocation
Mutation Animations
• What change do you notice?
Translocation 9 and 22
Name the mutation
• Animation Quiz 1
• (Not for the faint of heart) Human Mutants:
Mutant Human Organs : Video : Discovery
Channel Channel
Also could
have
substitution
Cystic Fibrosis Deletion
ALBINISM
Albinism is due to a mutation of the
melanin pigment gene. A one base
substitution results in only 1 amino
acid being in error.
AAGGTTCGGAGT (DNA)
type of mutation
Amino acids
AACGTTCGGAGT:____________________
AAGGTCTCGGAGT:____________________
AAGGTTCGAGT:_______________________
AAGGTTCGGAGT (DNA)
type of mutation
Amino acids
AACGTTCGGAGT:____________________
Substitution (C for the G)
AAGGTCTCGGAGT:____________________
Insertion (the C)
AAGGTTCGAGT:_______________________
Deletion (the G)
Chromosomal mutations
Affect the entire chromosome often fatal.
Mutagens can cut up DNA into
pieces.
When Repair mechanism
reassembles them, they may be in
the wrong order.
Oncogenes
Genes that when mutated
result in cancer.
EXAMPLE:
BRCA1 and BRCA2
Found to cause breast cancer
on 81-kb region of human
chromosome 17
NEWS FLASH!!!!
• Not every gene in your body is
translated into polypeptides all
the time.
OPERON
• A cluster of genes under the control of a
promoter (beginning of gene)
Promoter
• a nucleotide sequence that enables a
gene to be transcribed
Operator
• a segment of DNA that a repressor or
activator binds to
Lac Operon (promoter and
repressor)
• Animation
Quiz - The
Tryptophan
Repressor
LAC OPERON (start making
lactase)
• The lac Operon ANIMATION
• (If lactose is present, the repressor
attaches to it. The genes to break down
the lactose (lactase) can be made.)
• PICK ME VCAC: Molecular Processes:
Lac Operon: The Movie
HOX Genes
• Hox genes are defined by a DNA
sequence known as the
homeobox, which is a sequence
of 180 nucleotides
HOX GENES
• “Body Plan Genes”
HOX GENES: TELL THE BODY
WHERE TO PUT THE PARTS
Viral Infections
Viruses
• Nothing more than packaged genes
• Simple tools for geneticists
• HIV
EBOLA
Bacteriophage Infection (SEM)
Bacteriohage Infection
Every virus has two stages
• a dormant, particulate,
transmissible stage called the
virion stage
• an active, intracellular stage
called the infectious stage
Infectious Stage: Lytic Infection
1.attachment
2. Insertion of virus DNA
3. replication of virus components
4.packaging and assembly of new
virions
5. exit from cell –”lysis” bursts
The Lytic Cycle
Bacteriophage
protein coat
Bacteriophage DNA
Bacterial
chromosome
Bacteriophage attaches to
bacterium’s cell wall
Bacteriophage enzyme lyses the
bacterium’s cell wall, releasing
new bacteriophage particles that
can attack other cells.
Lytic
Cycle
Bacteriophage proteins and
nucleic acids assemble into
complete bacteriophage
particles
Bacteriophage takes over
bacterium’s metabolism, causing
synthesis of new bacteriophage
proteins and nucleic acids
Go to
Section:
Bacteriophage injects DNA
into bacterium
Bacteriophage
Bacteriophage DNA
Bacteriophage protein
LYTIC INFECTION
• Lytic Infection Animation
Lysogenic Infection
• The viral DNA becomes
integrated into the bacterial
DNA after infection. It is
replicated along with the host
DNA when the host reproduces.
The viral DNA is referred to as a
prophage.
A Lysogenic Infection
Bacterial
chromosome
Bacteriophage
DNA
Bacteriophage injects
DNA into bacterium
Bacteriophage DNA
(prophage) can exit the
bacterial chromosome
Lytic
Cycle
Bacteriophage enzyme lyses the
bacterium’s cell wall, releasing
new bacteriophage particles that
can attack other cells
Lysogenic
Cycle
Bacteriophage proteins and
nucleic acids assemble into
complete bacteriophage particles
Go to
Section:
Bacteriophage DNA
(prophage) may replicate
with bacterium for many
generations
Bacteriophage DNA
forms a circle
Prophage
Bacteriophage DNA
inserts itself into
bacterial chromosome
DIAGRAM COMPARISON
• Lytic and Lysogenic Infections
Virus Examples
• RNA instead of DNA: cold, flu, HIV, polio,
measles, mumps
• DNA viruses: herpes. Chicken pox,
hepatitis
• Herpes infections may flare up when
under stress, a cold, or sunburn
Ebola Virus
• Causes hemorrhagic fever
• Movie Outbreak
Hanta Virus
• Southwestern US mice carried it
cardiovascular collapse,
respiratory failure, and death
HIV
• Has 2 copies of RNA
• Is a retrovirus (RNA to DNA)
• Carry enzyme reverse transcriptase
Aids infected
cells
• HIV = Human
Immunodeficiency Virus
• AIDS = Acquired Immune
Deficiency Syndrome