protein synthesis biology 11 preap
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Protein Synthesis Biology 11 preAP. Overview and Application. Try This!. 1) One strand of DNA has the following sequence: T A C C G A C G G What is the corresponding sequence of RNA? - PowerPoint PPT PresentationTRANSCRIPT
Protein SynthesisBiology 11 preAP
Overview and Application
Try This!
1) One strand of DNA has the following sequence: T A C C G A C G G
What is the corresponding sequence of RNA?
2) If this new RNA is transported out of the nucleus directly to a ribosome, which of the three types of RNA is it?
OverviewMolecular Biology’s central dogma: replication, transcription, translation,
assembly: Howard Hugh’s Medicalhttp://www.youtube.com/watch?v=D3fOXt4MrOM
It is expected that you will know: The key terms gene expression, transcription, and
translation. How to explain the process of transcription How eukaryotic cells modify RNA after transcription The steps to translation How point mutations can change the amino acid
sequence
Overview
What are the stages of Protein Synthesis?
1) Transcription
2) mRNA Processing and Modification
3) Translation
Transcription
DNA is used as a template to form a molecule of single-stranded mRNA (messenger RNA)
http://vcell.ndsu.nodak.edu/animations/transcription/movie.htm
Transcription
Three steps:1) DNA unzips
2) Complimentary base pairing of ribonucleotides
3) Termination
Transcription – 1) Unzip
One section of DNA is unzipped (H-bond between nitrogen bases are broken) when RNA polymerase attaches to the promotor region of the DNA with the assistance of transcription factors.– Transcription Initation Complex
The DNA continues to be unzipped by RNA polymerase
Transcription – 2) Complimentary
RNA polymerase attatches free-floating ribonucleotides in the 5’-3’ direction – temporarily hydrogen bond with their complimentary
nucleotides on the DNA transcription unit– Covalent bond to the 3’ end of the previous ribonucleotide
Only one of the DNA strands is used as the template. Ex: DNA – A T C G
RNA –
Transcription - Termination
RNA polymerase reaches terminator sequence RNA polymerase detaches from DNA,
releasing single-stranded RNA strand DNA rewinds into its double helix
mRNA Processing
http://vcell.ndsu.nodak.edu/animations/mrnaprocessing/movie-flash.htm
Addition of 5’ cap Addition of poly-A tail RNA splicing
– Introns are removes, exons are spliced together by an enzyme called spliceosome
This enzyme has small nuclear RNA (snRNA) to help it work and is therefore referred to as a riboenzyme
Modified mRNA is transported out of the nucleus
Significance of mRNA splicing…
We have fewer than 25000 genes to make ~100000 proteins!– One gene can make different proteins due to
alternative mRNA splicing.
Translation
mRNA goes to the ribosome and is used as a template to synthesize a protein molecule.
http://vcell.ndsu.nodak.edu/animations/translation/movie.htm
Translation
Three Steps:
1) Initiation
2) Elongation
3) Termination
Translation – 1) Initiation
need start codon AUG
The first tRNA, with anticodon UAC and amino acid methionine temporarily binds to the first site
Translation – 2) Elongation
The second tRNA molecule attaches to the second site of translation.
Translation – 2) Elongation
The amino acid from the first tRNA is transferred to the amino acid on the second tRNA.
Translation – 2) Elongation
The first tRNA exits, the ribosome moves, a new tRNA enters, and the process is repeated.
Translation – 2) Elongation
The process is repeated many times, and a peptide, or strand of amino acids, is formed.
Translation – 3) Termination
The release factor enters.
Translation, or protein synthesis, ends.
Translation – 3) Termination
The completed polypeptide is released.
Translation - Application
What does this diagram represent?
- Translation
- ELONGATION
Polyribosomes
Many ribosomes transcribing the same mRNA
Very efficient!
Destination of Proteins
How does a protein “know” whether it to be used for a function in the cell, or bound for secretion?– Signal peptide: the first ~20 amino acids directs the
final destination
Application – table of mRNA codons (p 511)
Application
Consider the following DNA base sequence read from left to right:
T A C G C A A A A T G G
Determine the amino acid sequence that results from this DNA strand.
Application
DNA sequence:T A C G C A A A A T G G
mRNA sequence:A U G C G U U U U A C C
Animo acid sequence:
methionine – arginine – phenylalanine – threonine
Application
Which of the following is an anticodon of a molecule of tRNA carrying glycine?
A. G G A
B. C C U
C. C C T
D. C G C
Application
Which of the following is an anticodon of a molecule of tRNA carrying glycine?
Amino acid: glycine
mRNA codon: GGU/GGC/GGA/GGG
tRNA anticodon: CCA/CCG/CCU/CCC
Application
Which of the following is an anticodon of a molecule of tRNA carrying glycine?
A. G G A
B. C C U < ANSWER!C. C C T
D. C G C
Mutation Definitions
point mutation:– A change in the sequence of a base pair within a
gene
1) Base-pair substitutionA. Missense mutation – still amino acid
B. Nonsense Mutation – code for stop
2) Insertion and deletion – can cause frameshift mutation!
Definitions – Gene Mutations
frameshift mutationsTHE CAT ATE THE RAT – what if the “C” was deleted?
– The original DNA coded for which amino acids? DNA: TAC GGT TAG mRNA: AUG CCA AUC amino acids: methionine – proline - isoleucine
– The mutated DNA now codes for which amino acids? DNA: TAC CGG TTA G mRNA: AUG GCC AAU C animo acids: methionine – alanine - asparagine
Definitions - Gene Mutation
What effect does changing the amino acids have on the protein product?– Changes the shape.
Since shape determines function, it alters how the protein will function.
Proteins: Shape determines Function!
Definitions - Gene Mutation
Which has the potential for the most damage, deletions or subsitituations?
– Deletions! Frameshift
Definitions
Mutagens– Environmental influences that cause mutations
– Examples:Radiaton: radioactive elements, ultraviolet (UV) light, X rays
Organic chemicals: cigarette smoke, pesticides
Any Questions?
Closing
http://vcell.ndsu.nodak.edu/animations/transcription/movie.htm http://vcell.ndsu.nodak.edu/animations/translation/movie.htm http://vcell.ndsu.nodak.edu/animations/mrnaprocessing/movie-flash.htm
Molecular Biology’s central dogma: replication, transcription, translation, assembly: Howard Hugh’s Medicalhttp://www.youtube.com/watch?v=D3fOXt4MrOM
Epic:http://www.youtube.com/watch?v=u9dhO0iCLww