Transcript DNA

Protein Synthesis
From DNA to protein
And viruses
And bacteria
CENTRAL DOGMA:
From DNA to Protein
• OVERVIEW FIRST Central Dogma
Youtube (3:01)
• DNA wrapping, transcription, translation
Youtube (7:46)
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)
First Proposed by
• Francis Crick (1958)
• Later : Nirenberg said, "DNA
makes RNA makes protein."
Beadle and Tatum
REMEMBER US?
• 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 +
cytoplasm
• rRNA –ribosomal RNA –
plus protein makes up a
ribosome
ANIMATIONS
• McGraw-Hill Transcription Animation
• McGraw-Hill Translation Animation
Transcription: DNA to mRNA
McGraw Hill Transcription Animation
• DNA never leaves the nucleus
• It codes to mRNA to take the
message outside the nucleus
• TRANSCRIPTION YOUTUBE (1:53)
• Transcription (1:27)
RNA polymerase
(RNAP)
• The enzymes that
makes RNA from the
DNA template
DNA
RNAP
RNA
REMEMBER:
U replaces T in all RNA’s
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
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
• Coding from mRNA to making
protein (at the ribosome)
• DNA Translation Youtube (2:06)
TRANSLATION
• mRNA (genetic language) needs to
be translated into protein language
(chain of amino acids)
• Transcription Youtube (2:06)
tRNA
• transports amino
acids
to ribosomes
• There is a specific
amino acid for each
tRNA
• Anticodon for that
amino acid
Job of tRNA
• Complements the codon of mRNA
and picks up the appropriate amino
acid tRNA animation (1:29)
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)
McGraw Hill EPA 2:24
A P E Sites at the
Ribosome
Translocation
movement of
tRNA across the
ribosome
TRANSLATION Virtual Cell
Animation (Nice APE sites)
(3:32)
There are 20 Amino Acids
• These 20 are shared by all living
organisms
• What does CAC code for?
• histidine
Notice AUG codon means “start”
building a new protein. UAA,
UAG, UGA mean “stop’ building the
protein.
Translation Initiation
• mRNA attaches to the ribosome
(AUG –start codon)
Translation Elongation
tRNA brings amino acids to the
ribosome
Translation Termination
video 1:01
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)
transcription
translation
All mRNA’s start with AUG, so all
DNA genes start with______?
Answer
•Methionine
• Is always the STARTamino
acid
GENE REGULATION
pp. 210-11
• Remember that question on the
DNA Extraction lab: “Do all
cells in your body have the
same DNA?”
• YES
• Just not all genes are
expressing at the same time.
EXAMPLE: Lac operon
• E. coli used to produce
lactose-using enzymes:
• lacZ codes for β-galactosidase
• lacY for lactose permease
• lacA codes for galactoside
O-acetyltransferase
Gene Expression
• Gene promoter = where RNA polymerase
attaches and initiates transcription
• Operator = acts like a switch – between
promoter and genes
• Represser = turns off transcription-binds
to operator and blocks RNA polymerase
OPERON =
• Operator + represser +
promoter + genes
GENE REGULATION
turning on and off of genes
• Lac operon control 2:09
• McGraw Hill Lac Operon
• 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
Mutation Lingo
• Mutation = any change in
nucleotide sequence of DNA
• Reading frame = triplet grouping
• Mutagenesis = creation of
mutations
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.
FRAMESHIFT MUTATION (1:24)
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
What type of mutation is this?
• SILENT
What type of mutation is this?
• MISSENSE
What type of mutation is this?
• NONSENSE
Chromosome Mutations
has moved
Translocation
one segment
•
of a
chromosome
to a different
Chromosome
translocation
youtube
• Inversion
• Segment of a
same
chromosome is
turned end to
end
• Inversions 2:05
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:_______________________
AAGGTTCGGAGT (DNA)
type of mutation
Amino acids
AACGTTCGGAGT:Substitution(C for G)
AAGGTCTCGGAGT:_Insertion (the C)
AAGGTTCGAGT:__Deletion (the G)
Chromosomal mutations
Affect the entire chromosome often fatal.
We will look at this kind in
Chapter 9.
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
VIRUSES
a small infectious agent that
can replicate only inside the
living cells of an organism
Viruses
• Nothing more than packaged genes
• Simple tools for geneticists
• HIV
EBOLA
Viral Infections
Bacteriophage Infection (SEM)
Bacteriohage Infection
Every virus has two stages
• a dormant, particulate,
transmissible stage called the
virion stage (usually protein coat
+ DNA or RNA)
• 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
Viroid
• Virus in plants
Virion
• An entire virus particle,
consisting of an outer protein
shell called a capsid and an inner
core of nucleic acid
PRION
• an infectious agent composed of
protein in a misfolded form.
• EXAMPLE: Mad Cow Disease - BSE
Emerging Viruses
• a virus that has adapted and emerged as
a new disease/pathogenic strain
• EXAMPLES:
Influenza
• Hanta Virus
• Ebola
• Nipah
Why are viruses called
• GENES IN A BOX
• They are usually a genetic material (DNA
or RNA) inside a protein coat
Ebola Virus
• Causes hemorrhagic fever
• Movie Outbreak
Hanta Virus
• Southwestern US mice carried it
cardiovascular collapse,
respiratory failure, and death
HIV
•
•
•
•
Is the virus that causes AIDS
Has 2 copies of RNA
Is a retrovirus (RNA to DNA)
Carry enzyme reverse transcriptase
(codes backwards RNA to DNA)
Aids infected
cells
• HIV = Human
Immunodeficiency Virus
• AIDS = Acquired Immune
Deficiency Syndrome
BACTERIA
• Prokaryotic
• One-celled
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 DNA from
one bacterial cell to another