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 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 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