INITIATION

-holoenzyme (/w sigma) scans DNA for promoter regions... transcription begins at +1

-at -35 recognition sequence.. RNA polymerase binds to DNA

-at -10, separation of two strands occurs.... is A/T rich region (only 2 H bonds... weak interaction)

ELONGATION

-core enzyme comes into play.. (holoenzyme/sigma falls off).... moves along in 3'-5' direction on DNA strand, building 5' to 3' the mRNA

-RNA is same as non-template strand, but T becomes U

TERMINATION

-encounters G-C rich sequence, followed by a chain of U

- strong G-C area (forms hairpin loop)

***actual reading of gene begins at ATG region after +1 area!!!!****

INITIATION

-ribosome binding site (GGAGG) on mRNA... start codon (AUG) is Methyanine

ELONGATION

-reading codons... in groups of 3

TERMINATION

-stop codon..(UGA, UAA, UAG)

-1940s.. worked with Neurospora

1)biosynthesis occurs as a series of steps (a biosynthetic pathway)

2)Each step is catalyzed by a different enzyme

3)Each enzyme is encoded for by a particular gene

-auxotrophic - strains of organisms are strains which have developed a nutritional requirement through a mutation. As such, they are unable to complete that particular biosynthetic pathway because one orm ore o the genes controlling the pathway have been rendered inactive

-prototroph - or "wild type" is the parent strain from which the auxotroph has been derived. The prototrophic strain is able to complete the pathway and produce end product because the genetic information is complete

1)How many reaction steps are in the pathway?

2)What is the shape of the pathway (linear/branched)?

2)Which genes control which steps in the pathway?

mutual feeding can occur b/w strains with blocks on opposite branches, or b/w different phenotypes. This means that auxotrophs on opposite sides of the branches can feed on each other to complete biosynthetic pathways.