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Protein Synthesis
From DNA to protein
And viruses
And bacteria
Central Dogma
• You Tube Protein Synthesis (2:51)
• DNA Transcription and Protein Assembly (3:02) From DNA to
proteins
• FROM GENOTYPE TO
PHENOTYPE
(From DNA to proteins)
Beadle and Tatum
REMEMBER US?
George Beadle and Edward Tatum
during the late 1930s and early 1940s
• Using Neurospora crassa bread mold
determined "one gene one enzyme hypothesis"
Protein Synthesis Overview
get “Central Dogma” and
“Protein Synthesis” Worksheets
• DNA Replication, Transcription, Translation Youtube (8 mins)
Learn these Terms
• Transcription = DNA → mRNA
• Translation = mRNA → protein
Three Bases Lingo
• DNA
Triplet
ATC
• mRNA
Codon
UAG
tRNA
Anti-codon
AUC
The 3 RNA’s
• mRNA – messenger RNA
– codes from DNA in the
nucleus to take the genetic
code to the ribosome in
the cytoplasm
• tRNA – transfer RNA –
brings a specific amino
acid to the ribosome
• rRNA –ribosomal RNA –
plus protein makes up a
ribosome
Transcription: DNA to mRNA
• DNA never leaves the nucleus
• It codes to mRNA to take the
message outside the nucleus
• TRANSCRIPTION YOUTUBE (1:53)
RNA polymerase
(RNAP)
• The enzymes that
makes RNA from the
DNA template
DNA
RNAP
RNA
Not all RNA nucleotides make the cut:
Introns and Exons
• Primary mRNA = exons +
introns
• INTRONS = discarded, noncoding
region of mRNA
• EXONS = the coding regions, spliced
together RNA are called also =
Mature mRNA
• RNA Splicing
Youtube (1:38)
SPLICING RNA
Or Primary
RNA
Mature mRNA
SPLICING ANIMATION
snRNP’s Spliceosome
Seriously detailed splicing youtube (1:39)
McGraw-Hill How Splicesosomes Process RNA
• Before the mRNA leaves the
nucleus, the introns are removed,
and the exons are spliced together.
Exons leave the nucleus
Mature mRNA leaves
Transcription Initiation Control
Transcription Promotors
• DNA sequences at start site (recognize
TATA BOX)
TATA
• RNA polymerase and accessory proteins
(transcription factors) bind to the promoter
to initiate production of an mRNA
transcription.
Transcription Terminator
• mRNA is cut free from DNA
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
• mRNA (genetic language) needs to
be translated into protein language
(chain of amino acids)
• Translation Youtube (2:06)
TRANSLATION
• Coding from mRNA to making protein
(at the ribosome)
• DNA Translation Youtube (2:06)
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
acid
ANIMATION:
Animation of
Translation
Note the A P E sites
Central Dogma youtube (3:03)
• A site – Amino acid is
dropped off
• P site – Polypeptide
builds
• E site – tRNA exits
(after giving its amino
acid to building
polypeptide chain)
APE sites of Ribosome
youtube (1:31)
A P E Sites at the
Ribosome
Translocation:
movement of
tRNA across the
ribosome
Notice AUG codon means “start”
building a new protein. UAA,
UAG, UGA mean “stop’ building the
protein.
There are 20 Amino Acids
• These 20 are shared by all living
organisms
• What does CAC code for?
• histidine
Translation Initiation
• mRNA attaches to the ribosome (AUG –
start codon)
Translation Elongation
tRNA brings amino acids to the ribosome
Translation Termination
mRNA reaches one of the STOP codons
• Bond breaks the last tRNA and its amino
acid to release the polypeptide bond
Cooooool Protein Synthesis 3-D
• CENTRAL DOGMA (2:52)
All mRNA’s start with AUG, so all
DNA genes start with______?
Answer
•Methionine
• 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
• Mutagen =any source of mutation is
a physical or chemical agent
–EX: X-rays
–UV light
–cigarette components
–Hazardous chemicals
Mutagens
Mutation Animations
• BBC - Education Scotland - Higher Bitesize Revision - Biology
- Genetics and adaptation - Mutations: Revision 2
• EXPLAIN HOW EACH MUTATION IS DIFFERENT
FROM THE ORIGINAL DNA SEQUENCE
Gene (point)mutations
SUBSTITUTION – Replace one base for
another. Minimal effect
ADDITION – Adding a base
DELETION – removing a base
Addition/deletions cause a complete
Frame Shift that affects the whole
gene.
Mutation Lingo
• Mutation = any change in
nucleotide sequence of DNA
• Reading frame = triplet grouping
• Mutagenesis = creation of
mutations
More Mutation Lingo
• Nonsense mutation = change an
amino acid into a STOP codon
• Missence mutation = change the
amino acid coding
• Silent mutation = no change in
protein product
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
Translocation
Translocation 9 and 22
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:_______________________
ANSWER-
• Substitution (C for the G)
• Insertion (the C)
• 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
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
F Factor
• Fertility factor
• Allows one bacterium to carry genes to
another by conjugation
Sex pili
Bacterium Plasmid
• Circular DNA in bacteria
• Extra genes, not essential for bacterial
survival
Transformation
• Uptake of DNA from another bacteria cell
Conjugation
• Physical union of two bacterial cells to
transfer DNA
R Plasmid
• Contain genes that are resistant to many
antibiotics
Transduction
• Some viruses move bacterial from one
bacterial cell to another