Post on 14-Jan-2022
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CHAPTER 17PROTEIN SYNTHESIS
• DNA: NUCLEIC ACID, DOUBLE STRAND, PO4, DE-OXYRIBOSE SUGAR.
• BASE PAIRS (N)• T=THYMINE• A=ADENINE• C= CYTOSINE• G=GUANINE
• RNA: NUCLEIC ACID, SINGLE STRAND, PO4, RIBOSE SUGAR.
• BASE PAIRS (N)• U = URACIL• A=ADENINE• C=CYTOSINE• G=GUANINE
2Fig. 14.6, p. 228
URACIL(U)
base with a single-ring structure
phosphate group
sugar (ribose)
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POINTS ABOUT TRANSCRIPTION
• NEED RNA POLYMERASE• CODES FOR 20 AMINO ACIDS• CODON:SERIES OF TRIPLET BASE
PAIRS.• 64 CODONS, 60 FOR AA, OTHERS
FOR STARTS/STOPS.• INTRONS=NON-CODING• EXONS= CODING FOR RNA
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PROTEIN TRANSCRIPTION
• NUCLEUS• RNA POLYMERASE CODES TO DNA• DNA TRANSCRIBES TO m-RNA• INTRONS SNIPPED OUT• EXONS KEPT IN CODE• MUTATIONS/MUTONS/MUTAGENIC
AGENTS
5Fig. 14.9, p. 229
unit of transcription in a DNA strand
exon intron
mature mRNA transcript
poly-Atail
5’
5’ 3’
3’
(snipped out) (snipped out)
exon exonintron
cap
transcription into pre-mRNA
3’ 5’
6Fig. 14.8, p. 228-229
3’5’
growing RNA transcript5’
3’ 5’
3’
direction of transcription
RNA polymerase
sugar-phosphate backbone of one strand of nucleotides in a DNA double helix
sugar-phosphate backbone ofthe other strand of nucleotides
part of the sequence of base pairs in DNA
transcribed DNA winds up again
DNA to be transcribed unwinds
Newly forming RNA transcript
The DNA template at the assembly site
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PROTEIN TRANSLATION
• m-RNA GOES THRU RIBOSOME.
• RIBOSOME IS r-RNA,CODE THREADS THRU RIBOSOME.
• AREA OF RIBOSOME BOUND TO tRNA
• 20 TYPES OF AA• ANTICODON ON
ONE END OF t-RNA.
• AA ON OTHER END OF t-RNA
• AA ATTACH TO EACH OTHER IN PEPTIDE BOND
• FORM PROTEINS
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+
Fig. 14.13, p. 231
platform for chain assembly
9Fig. 14.12, p. 231
codon in mRNA
anticodon
amino acid OH
amino acidattachment site
anticodon
tRNA MOLECULE
amino acid attachment site
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Figure 17.13b The structure of transfer RNA (tRNA)
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Binding site for mRNA
P(first
binding site fortRNA)
A (second binding site fortRNA)
Fig. 14.14a, p. 232
12Fig. 14.14b, p. 233
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13Fig. 14.18, p. 237
TRANSCRIPTION Unwinding of gene regions of a DNA molecule
Pre mRNATranscript Processing
mRNA rRNA tRNA
TRANSLATION
FINAL PROTEIN
Destined for use in cell or for trasport
Convergence of RNAs
Synthesis of apolypetide chain at binding sites formRNA and tRNAon the surface of an intact ribosome
Cytoplasmicpools of amino acids,tRNAs, and ribosomalsubunits
Mature mRNAtranscripts
proteinsubunits
ribosomalsubunits
maturetRNA
14animation
Click to view animation.
15Fig. 14.5, p. 227
VALINE
HISTIDINE
LEUCINE
PROLINE THREONINE
GLUTAMATE GLUTAMATE
VALINE
HISTIDINE
LEUCINE
PROLINE THREONINE
GLUTAMATE
VALINE
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mRNA transcribed from the DNA
PART OF PARENTAL DNA TEMPLATE
resulting amino acid sequence
altered message in mRNA
A BASE INSERTION (RED) IN DNA
the altered amino acid sequence
ARGININE GLYCINE TYROSINE TRYPTOPHAN ASPARAGINE
ARGININE GLYCINE LEUCINE GLUTAMATELEUCINE
Fig. 14.16, p. 234
17Fig. 14.17, p. 235
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Figure 17.2 Overview: the roles of transcription and translation in the flow of genetic information (Layer 5)
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Figure 17.3 The triplet code
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TRANSCRIPTION AND TRANSLATION
• C DNA. ATC-GCG-TAT• m-RNA. UAG-CGC-AUA• t-RNA. AUC-GCG-UAU• AMINO
ACID ISO-ALA-TYR• PEPTIDE
BONDS/POLYPEPTIDES/PROTEINS
21Fig. 14.11, p. 230
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TYPES OF PROTEINS
• ENZYMES/HELICASE• CARRIER/HEMOGLOBIN• IMMUNOGLOBULIN/ANTIBODIES• HORMONES/STEROIDS• STRUCTURAL/MUSCLE• IONIC/K+,Na+• all regulate things put together/”critter”
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Figure 17.22 Coupled transcription and translation in bacteria
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VALINE
HISTIDINE
LEUCINE
PROLINE THREONINE
GLUTAMATE
VALINE
original base triplet in a DNA strand
As DNA is replicated, proofreadingenzymes detect the mistake andmake a substitution for it:
a base substitution within the triplet (red)
One DNA molecule carries the original,unmutated sequence
The other DNAmolecule carries a gene mutation
POSSIBLE OUTCOMES:
OR
Fig. 14.15, p. 234
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Figure 17.25 A summary of transcription and translation in a eukaryotic cell