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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