chapter 3, part c central dogma of molecular biology from genes to protein
TRANSCRIPT
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Chapter 3, part C
Central Dogma of Molecular Biology
From Genes to Protein
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transcription
translation
RNA Processing
mRNA
1o transcript
mRNA
polypeptide
ribosome
ribosome
mRNA
2o transcript
Central Dogma of Molecular BiologyEukaryotic Cell
Transcription: synthesis of mRNA from DNA by RNA polymerase protein
- Two steps:
1. creating a 1o mRNA transcript
2. RNA processing (editing) to create 2o mRNA transcript
Translation: ribosomes link together amino acids to create a polypeptide from the 2o mRNA code
Polypeptide then coils into a specific 3-D shape to form a functional protein
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Triplet-code Instructions for a polypeptide
Transcription
Translation
A C C A A A C C G A G T
U G G U U U G G C U C A
trp phe gly ser
DNA
mRNA
polypeptide
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Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 3.34b: An overview of transcription, p. 106.
RNAnucleotides
RNA polymerase
Unwindingof DNA
Coding strand
Rewinding of DNA
mRNARNA-DNAhybrid region
Template strand
(b)
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3 RNA Players Involved in Translation
mRNA = DNA transcripttRNA = type of RNA that carries the amino acids to the ribosome
rRNA = RNA that, combined with protein, makes up the structural component of a ribosome
Central Dogma
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Redundancy in AA
- Notice…several codons code for the same AA
Redundancy helps to minimize errors in protein synthesis due to
mutations
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Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 3.36: Translation, p. 108.
mRNA transcription and processing
mRNA moves out of nucleus
Amino acids
tRNA
tRNA anticodon
ribosome
Released mRNA
mRNA
Template strandof DNA
RNA polymeraseNucleus
A growing polypeptide chain of amino acids is created
Polypeptide eventually folds into a specific protein
Amino acid is attached to each species of tRNA by an enzyme
ribosome translates mRNA by moving along the mRNA and matching codons with anticodons of tRNA
tRNA carry amino acids to be peptide bonded together
Codon
PCG
G CC C A UU AUG
E A
Ile
Ala
Phe
Ser
GlyMet
Ile
AAGUA U
UAU
1
4
3
2
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Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 3.37: Polyribosomes, p. 109.
Ribosome
Completedpolypeptide
Peptide chain
Ribosomalunits
mRNA
mRNARibosome
1
1
1
1
11
2
2
2
2
3
3
3
4
45
(a) (b)
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Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 3.38: Information transfer from DNA to RNA, p. 110.
DNAmolecule
Gene 1
Gene 3
Gene 5
DNA base sequence (triplets)of the gene coding for thesynthesis of a particularpolypeptide chain
Base sequence (codons) ofthe transcribed mRNA
Consecutive base sequencesof tRNA anticodons capableof recognizing the mRNAcodons calling for theamino acids they transport
Amino acid sequence of thepolypeptide chain
1 2 3 4 5 6 7 8 9
Codons
Triplets
tRNA
1 2 3 4 5 6 7 8 9
StartStop;
detach
Met Pro Ser Leu Lys Gly Arg Phe
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