Chapter 4
Transcription and
Translation
The Central Dogma
Overview of transcription
Figure 4-10
Overview of transcription
Figure 4-10
Types of RNAs transcribed
Transcription of a bacterial gene
Starting and stopping transcription of a bacterial gene
Overview of RNA processing in eukaryotes
Figure 4-13/14
Intron Splicing
Different proteins are produced from the same
gene by alternative RNA splicing
Figure 4-15
Figure 4-12
Repressors and Activators
Transcription in Eukaryotes
Gene regulatory proteins can bind to distant gene regulatory
sequences and regulate transcription.
The three roles of RNA in protein synthesis
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Three types of RNA molecules perform different but
complementary roles in protein synthesis (translation)
Messenger RNA (mRNA) carries information copied from DNA in
the form of a series of three base “words” termed codons
Transfer RNA (tRNA) deciphers the code and delivers the specified
amino acid
Ribosomal RNA (rRNA) associates with a set of proteins to form
ribosomes, structures that function as protein-synthesizing
machines
The roles of RNA in protein synthesis
Figure 4-19
The genetic code is a triplet code
The genetic code can be read in different frames
Figure 4-20
Translation is a two-step decoding process
Figure 4-21
The structure of tRNA specifies its decoding function
Figure 4-22
Nonstandard base pairing often occurs between
codons and anticodons
Figure 4-23
Ribosome structure in prokaryotes & eukaryotes
Figure 4-24
Image reconstruction of an E. coli ribosome
Figure 4-27
Stepwise formation of proteins on ribosomes
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Translation occurs in three stages: initiation, elongation, and
termination
Initiation
Figure 4-25
Initiation continued
Figure 4-25
During elongation each incoming aminoacyl-tRNA
moves through three ribosomal sites
Figure 4-26
During elongation each incoming aminoacyl-tRNA
moves through three ribosomal sites
Figure 4-26
Protein synthesis is terminated by release factors
when a stop codon is reached
Figure 4-29
Simultaneous translation by multiple ribosomes and
their rapid recycling increases the efficiency of
protein synthesis
Figure 4-31