Transcription and RNA Processing
description
Transcript of Transcription and RNA Processing
![Page 1: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/1.jpg)
Transcription and RNA Processing
![Page 2: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/2.jpg)
![Page 3: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/3.jpg)
RNA Synthesis And Transport in Eukaryotes
Method: Pulse-Chase Labeling
At first, labeled RNA is exclusively in the nucleus.
Later, the labeled RNA is found in the cytoplasm.
![Page 4: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/4.jpg)
Awful representation
![Page 5: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/5.jpg)
Correct Representation of DNA
![Page 6: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/6.jpg)
RNA make a new “top strand”
![Page 7: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/7.jpg)
![Page 8: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/8.jpg)
Modifications to Eukaryotic pre-mRNAs
A 7-Methyl guanosine cap is added to the 5’ end of the primary transcript by a 5’-5’ phosphate linkage.
A poly(A) tail (a 20-200 nucleotide polyadenosine tract) is added to the 3’ end of the transcript. The 3’ end is generated by cleavage rather than by termination.
When present, intron sequences are spliced out of the transcript.
![Page 9: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/9.jpg)
Eukaryotes Have Three RNA Polymerases
Pol II is the only Polymerase that is routinely studied.Pol I and Pol III are very complicated.
![Page 10: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/10.jpg)
miRNAproduction
![Page 11: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/11.jpg)
A Typical RNA Polymerase II Promoter
![Page 12: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/12.jpg)
What does the word Promoter mean?
It is the place at which RNA Pol II binds.But the word is incorrectly used to describeEnhancers plus Promoter.
![Page 13: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/13.jpg)
Initiation by RNA Polymerase II
![Page 14: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/14.jpg)
![Page 15: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/15.jpg)
![Page 16: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/16.jpg)
TFIID recognition site is TATAA
How often is this site found in the genome? 1/45
Once every 1000 nucleotides 109 nucleotides or 106 times
![Page 17: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/17.jpg)
![Page 18: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/18.jpg)
![Page 19: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/19.jpg)
More CellsBut on a per cellBasis expression levels of -gal is about the same
Transient transfection
![Page 20: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/20.jpg)
Stable transfection
![Page 21: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/21.jpg)
The 7-Methyl Guanosine(7-MG) Cap
![Page 22: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/22.jpg)
The 3’ Poly(A) Tail
AAUAAA
![Page 23: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/23.jpg)
Interrupted Genes in Eukaryotes: Exons and Introns
Most eukaryotic genes contain noncoding sequences called introns that interrupt the coding sequences, or exons. The introns are excised from the RNA transcripts prior to their transport to the
cytoplasm.
![Page 24: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/24.jpg)
Removal of Intron Sequences by RNA Splicing
The noncoding introns are excised from gene transcripts by several
different mechanisms.
![Page 25: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/25.jpg)
Excision of Intron Sequences
![Page 26: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/26.jpg)
Splicing
Removal of introns must be very precise. Conserved sequences for removal of the introns of
nuclear mRNA genes are minimal.– Dinucleotide sequences at the 5’ and 3’ ends of introns.– An A residue about 30 nucleotides upstream from the 3’
splice site is needed for lariat formation.
![Page 27: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/27.jpg)
Types of Intron Excision The introns of tRNA precursors are excised by precise
endonucleolytic cleavage and ligation reactions catalyzed by special splicing endonuclease and ligase activities.
The introns of nuclear pre-mRNA (hnRNA) transcripts are spliced out in two-step reactions carried out by spliceosomes.
![Page 28: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/28.jpg)
The Spliceosome
Five snRNAs: U1, U2, U4, U5, and U6
Some snRNAs associate with proteins to form snRNAs (small nuclear ribonucleoproteins)
![Page 29: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/29.jpg)
![Page 30: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/30.jpg)
What are Logo plots?
![Page 31: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/31.jpg)
Logo fora) Splice acceptor
b) Splice Donor
c) Initiator Met
![Page 32: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/32.jpg)
AG/GTAG/GT CAG/NTCAG/NT
exon 1 exon 1 intron 1 intron 1 exon 2exon 2
9 8 7 6 5 4 3 2 1 1 2 4 3 2 1 1 2 3 4 5 6
![Page 33: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/33.jpg)
Chapter 12Translation and the Genetic Code
![Page 34: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/34.jpg)
Protein Structure
Proteins are complex macromolecules
composed of 20 (?)
different amino acids.
![Page 35: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/35.jpg)
Amino Acids Proteins are made of polypeptides. A polypeptide is a long chain of amino acids.
Amino acids have a free amino group, a free carboxyl group, and a side group (R).
![Page 36: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/36.jpg)
![Page 37: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/37.jpg)
Peptide Bonds
Amino acids are joined by peptide bonds. The carboxyl group of one amino acid is
covalently attached to the amino group of the next amino acid.
![Page 38: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/38.jpg)
Protein Synthesis: Translation
The genetic information in mRNA molecules is translated into the amino acid sequences of
polypeptides according to the specifications of the genetic code.
![Page 39: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/39.jpg)
The Macromolecules of Translation
Polypeptides and rRNA molecules Euk: 28S, 18S, 5.8S, 5S
Amino-acid Activating Enzymes tRNA Molecules Soluble proteins involved in polypeptide
chain initiation, elongation, and termination
![Page 40: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/40.jpg)
Why does one need the ribosome to translate mRNA?
![Page 41: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/41.jpg)
RibosomesWhat does “S” mean? Why do sizes get bigger?
![Page 42: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/42.jpg)
The Nucleolus
In eukaryotes, the nucleolus is the site of rRNA synthesis and ribosome assembly
![Page 43: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/43.jpg)
Synthesis and Processing of the 30S rRNA Precursor in E. coli
ProKaryotenumbers
![Page 44: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/44.jpg)
Synthesis and Processing of the 45S rRNA Precursor in Mammals
![Page 45: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/45.jpg)
rRNA Genes rRNA Genes in E. coli
– Seven rRNA genes distributed among three sites on the chromosome
rRNA Genes in Eukaryotes– rRNA genes are present in hundreds to thousands
of copies– The 5.8S-18S-28S rRNA genes are present in
tandem arrays in the nucleolar organizer regions of the chromosomes.
– The 5S rRNA genes are distributed over several chromosomes.
![Page 46: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/46.jpg)
Transfer RNAs (tRNAs) tRNAs are adapters
between amino acids and the codons in mRNA molecules.
The anticodon of the tRNA base pairs with the codon of mRNA.
The amino acid is covalently attached to the 3’ end of the tRNA.
tRNAs often contain modified nucleosides.
![Page 47: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/47.jpg)
What is Inosine?
![Page 48: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/48.jpg)
![Page 49: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/49.jpg)
Inosine
![Page 50: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/50.jpg)
tRNA Structure
![Page 51: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/51.jpg)
Specificity of tRNAs
tRNA molecules must have the correct anticodon sequence.
tRNA molecules must be recognized by the correct aminoacyl-tRNA synthetase.
tRNA molecules must bind to the appropriate sites on the ribosomes.
![Page 52: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/52.jpg)
Codon Specificity Resides in the tRNA, Not the Attached Amino Acid.
![Page 53: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/53.jpg)
tRNA Binding Sites on the Ribosome (Ribosme moves
like an enzyme)
![Page 54: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/54.jpg)
Stages of Translation
Polypeptide Chain InitiationChain ElongationChain Termination
![Page 55: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/55.jpg)
Translation Initiation in E. coli
30S subunit of the ribosomeInitiator tRNA (tRNAMet)mRNAInitiation Factors IF-1, IF-2, and IF-3One molecule of GTP50S subunit of the ribosome
![Page 56: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/56.jpg)
![Page 57: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/57.jpg)
![Page 58: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/58.jpg)
The Shine-Dalgarno Sequence
![Page 59: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/59.jpg)
Translation Initiation in Eukaryotes
The amino group of the methionine on the initiator tRNA is not formylated.
The initiation complex forms at the 5’ terminus of the mRNA, not at the Shine-Dalgarno/AUG translation start site.
The initiation complex scans the mRNA for an AUG initiation codon. Translation usually begins at the first AUG.
Kozak’s Rules describe the optimal sequence for efficient translation initiation in eukaryotes.
![Page 60: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/60.jpg)
![Page 61: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/61.jpg)
Polypeptide Chain Elongation An aminoacyl-tRNA binds to the A site of the
ribosome. The growing polypeptide chain is transferred from
the tRNA in the P site to the tRNA in the A site by the formation of a new peptide bond.
The ribosome translocates along the mRNA to position the next codon in the A site. At the same time,– The nascent polypeptide-tRNA is translocated from the A
site to the P site.– The uncharged tRNA is translocated from the P site to
the E site.
![Page 62: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/62.jpg)
![Page 63: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/63.jpg)
![Page 64: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/64.jpg)
![Page 65: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/65.jpg)
![Page 66: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/66.jpg)
![Page 67: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/67.jpg)
![Page 68: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/68.jpg)
Elongation of Fibroin Polypeptides (A mRNA can have multiple Ribosomes
![Page 69: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/69.jpg)
Polypeptide Chain Termination
Polypeptide chain termination occurs when a chain-termination codon (stop codon) enters the A site of the ribosome.
The stop codons are UAA, UAG, and UGA. When a stop codon is encountered, a release
factor binds to the A site. A water molecule is added to the carboxyl
terminus of the nascent polypeptide, causing termination.
![Page 70: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/70.jpg)
No tRNA exists for stop codons!
![Page 71: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/71.jpg)
![Page 72: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/72.jpg)
Dissociation upon finish of protein synthesis
![Page 73: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/73.jpg)
The Genetic Code
The genetic code is a nonoverlapping code, with each amino acid plus
polypeptide initiation and termination specified by RNA codons composed of
three nucleotides.
![Page 74: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/74.jpg)
Properties of the Genetic Code
The genetic code is composed of nucleotide triplets.
The genetic code is nonoverlapping. (?) The genetic code is comma-free. (?) The genetic code is degenerate. (yes) The genetic code is ordered. (5’ to 3’) The genetic code contains start and stop
codons. (yes) The genetic code is nearly universal. YES :)
![Page 75: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/75.jpg)
A Triplet Code*
![Page 76: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/76.jpg)
A Single-Base Pair Insertion Alters the Reading Frame*
![Page 77: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/77.jpg)
A suppressor mutation restores the original reading frame.*
![Page 78: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/78.jpg)
Insertion of 3 base pairs does not change the reading
frame.*
![Page 79: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/79.jpg)
Evidence of a Triplet Code:In Vitro Translation Studies
Trinucleotides were sufficient to stimulate specific binding of aminoacyl-tRNAs to ribosomes.
Chemically synthesized mRNAs containing repeated dinucleotide sequences directed the synthesis of copolymers with alternating amino acid sequences.
mRNAs with repeating trinucleotide sequences directed the synthesis of a mixture of three homopolymers.
![Page 80: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/80.jpg)
Deciphering the Genetic Code
![Page 81: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/81.jpg)
You must know single letter codes and some triplets!
![Page 82: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/82.jpg)
The Genetic Code
Initiation and termination Codons– Initiation codon: AUG– Termination codons: UAA, UAG, UGA
Degeneracy: partial and completeOrderedNearly Universal (exceptions:
mitochondria and some protozoa)
![Page 83: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/83.jpg)
Key Points
Each of the 20 amino acids in proteins is specified by one or more nucleotide triplets in mRNA. (20 amino acids refers to what is attached to the tRNAs!)
Of the 64 possible triplets, given the four bases in mRNA, 61 specify amino acids and 3 signal chain termination. (have no tRNAs!)
![Page 84: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/84.jpg)
Key Points The code is nonoverlapping, with each
nucleotide part of a single codon, degenerate, with most amino acids specified by two to four codons, and ordered, with similar amino acids specified by related codons.
The genetic code is nearly universal; with minor exceptions, the 64 triplets have the same meaning in all organisms. (this is funny)
![Page 85: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/85.jpg)
Do all cells/animals make the sameRepertoire of tRNAs?
![Page 86: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/86.jpg)
The Wobble Hypothesis:Base-Pairing Involving the Third
Base of the Codon is Less Stringent.
![Page 87: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/87.jpg)
Base-Pairing with Inosine at the Wobble Position
![Page 88: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/88.jpg)
Suppressor Mutations Some mutations in tRNA genes alter the
anticodons and therefore the codons recognized by the mutant tRNAs.
These mutations were initially detected as suppressor mutations that suppressed the effects of other mutations.
Example: tRNA mutations that suppress amber mutations (UAG chain-termination mutations) in the coding sequence of genes.
![Page 89: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/89.jpg)
Making a (UAG) Mutation
![Page 90: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/90.jpg)
Translation of an amber (UAG) Mutation in the Absence of a
Suppressor tRNA
![Page 91: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/91.jpg)
Translation of an amber Mutation in the Presence of a Suppressor tRNA
Note it is amber su3…why?????????
![Page 92: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/92.jpg)
Translation of an amber Mutation in the Presence of a Suppressor tRNA
If there was a single tRNATyr gene, then could onehave a amber supressor of it?
![Page 93: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/93.jpg)
Historical Comparisons
Comparison of the amino acid sequence of bacteriophage MS2 coat protein and the nucleotide sequence of the gene encoding the protein (Walter Fiers, 1972).
Was this first???? Sickle-cell anemia: comparison of the
sequence of the normal and sickle-cell alleles at the amino acid level and at the nucleotide level.
![Page 94: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/94.jpg)
Are the proteins produced a pure reflection of the mRNA
sequence????
tRNA environment, protein modifications post-translationally
![Page 95: Transcription and RNA Processing](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813e72550346895da886ce/html5/thumbnails/95.jpg)
RNApol IITATAA
CCATGG (Nco I site and Kozak Rule)ATG
AGGT….spliceGT……………A………polypyrimidine AG
PolyA recog sequenceAATAAA
The Reasons why ATG is a single codonand TGG is a single codon.
To Know for Exam