chapter 36: RNA synthesis and regulation in bacteria

transcription

synthesis of RNA from a DNA template

RNA polymerase has the following requirements:

1. DNA template

2. Activated precursors: ATP, GTP, UTP, and CTP

3. Mg (II)

template (antisense) strand

used as template for RNA synthesis and is complementary to both mRNA and coding strand

coding (sense) strand

has the same sequence as the RNA (except T for U). not used for reading.

messenger RNA (mRNA)

encodes the information for the synthesis of protein

transfer RNA (tRNA)

brings correct amino acid to ribosome

ribosomal RNA (rRNA)

helps to form ribosomes

explain three stages of RNA synthesis

1. initiation: promoter sites direct RNA polymerase to proper site of initiation. regulatory proteins called transcription factors bind to promoter regions and help RNA pol. RNA pol unwinds about 17 bP to form open promoter complex

2. elongation: synthesizes RNA in 5’ to 3’ direction at the transcription bubble

3. termination: two main mechanisms. RNA hairpin followed by several uracil residues terminates (protein independent). Rho protein binds RNA and pulls it away from RNA pol through ATPase activity (protein dependent)

ribonuclease III

cleaves out precursors of rRNA

beta galactosidase

hydrolyzes lactose into galactose and glucose

explain DNA components of regulatory system

regulator gene: encodes a repressor

operator site: DNA sequence where repressor binds

structural genes: codes for enzyme

inducer: removes repressor from operator

riboswitches

RNA structures built into mRNA that terminates transcription (ex. FMN)