microbiology Exam #4

inducer

A specific small molecule that disable the repressor in an operon.

constitutive

genes that are always expressed - code for things that are always needed, like enzymes for glycolysis.

structural genes

genes that code for proteins in operon

operons

genes that coordinate the regulation of gene expression

missense mutation

results in amino acid substitution EX= AAA to AAU = different amino acids (Lsy-Asn)

lactose presence in lac operon

acts as an inducer lac repressor is released from operator initiates transcription at slow rate.

mutagens

are environmental agents that increase the mutation rate• e.g.=chemicals, radiation• some have very specific effects

Mutations

are heritable changes In DNA sequence

transformation

bacteria pickup DNA from environment

cyclic AMP (cAMP)

A compound formed from ATP that acts as a second messenger. -binds to an activator (CAP)

silent mutation

A mutation that changes a single nucleotide, but does not change the amino acid created. EX= AAA to AAG= same amino acid (Lys).

sex pilus

A thin connection between two bacteria through which genetic material passes during conjugation.

lactose acts as

an inducer

operator

binding site for repressor protein

nonsense mutation

changes code from an amino acid to a stop codon. EX= GTC to TAG = UAG which is a stop codon.

regulatory genes

code for activators or repressors that fall outside the operon.

repressed genes are

expressed except when their expression is inhibited by repressors.

spontaneous mutation

occur naturally during DNA replication

frameshift mutation

one or more nucleotides are deleted or inserted. -changes all downstream amino acids (unless a multiple of 3 nucleotides is added/deleted).

control region of operon

promoter and operator

contents of an operon

promoter, operator, structural genes.

point mutation

replaces one nucleotide with another. Can be (silent, nonsense, or missense).

Promoter

specific region of a gene where RNA polymerase can bind and begin transcription

absence of lactose in lac operon

the repressor binds to the operator, preventing transcription.

horizontal gene transfer

the transfer of DNA from one bacteria to another in the same generation

transduction

transfer of DNA by virus(bacteriophage)

conjugation

transfer of plasmids during direct cell-to-cell contact.

why is cAMP produced

when energy levels are low. it stimulates RNA polymerase activity and increases RNA synthesis.

mating bridge

when sex pilus of one prokaryote latches onto another pulls it in