Chapter 3, part C

Central Dogma of Molecular Biology

From Genes to Protein

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

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

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)

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

Redundancy in AA

- Notice…several codons code for the same AA

Redundancy helps to minimize errors in protein synthesis due to

mutations

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

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)

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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