Protein Synthesis
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Transcript of Protein Synthesis
Protein SynthesisFrom 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
RNARNAP
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
Mature mRNA
Or Primary RNA
SPLICING ANIMATIONsnRNP’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)
• RNA polymerase and accessory proteins (transcription factors) bind to the promoter to initiate production of an mRNA transcription.
TATA
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 sitesCentral 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?
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
Thalidomide baby…
• 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• Segment of a same chromosome
is turned end to end
has moved one segment of a chromosome to a different chromosome
Translocation
Translocation 9 and 22
Cystic Fibrosis Deletion
Albinism is due to a mutation of the melanin pigment gene. A one base substitution results in only 1 amino acid being in error.
ALBINISM
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
Bacteriophage enzyme lyses thebacterium’s cell wall, releasingnew bacteriophage particles thatcan attack other cells.
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
Bacteriophage injects DNA into bacterium
Bacteriophage attaches to bacterium’s cell wall
Bacteriophage
Bacteriophage DNA
Bacteriophage protein
Bacteriophage protein coat
Bacteriophage DNA
Bacterialchromosome
Lytic Cycle
The Lytic Cycle
Go to Section:
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.
Bacteriophage proteins and nucleic acids assemble into complete bacteriophage particles
Bacteriophage enzyme lyses the bacterium’s cell wall, releasing new bacteriophage particles that can attack other cells
Bacteriophage DNA inserts itself into bacterial chromosome
Bacteriophage DNA (prophage) may replicate with bacterium for many generations
Bacteriophage DNA (prophage) can exit the bacterial chromosome
Bacteriophage DNA forms a circle
Bacteriophage DNA
Bacterialchromosome
Bacteriophage injects DNA into bacterium
Prophage
Lytic Cycle
Lysogenic Cycle
A Lysogenic Infection
Go to Section:
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