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