moves along strand of DNA (template strand) causing nucleotides to join complementary bases
what is the function of DNA helicase?
separates the two strands of DNA by breaking H bonds.
what are transcription factors?
proteins which move in cytoplasm and bind to DNA and also control attachment of RNA polymerase to the DNA
some transcriptions factors are in all cells and some are only in certain types of cells
some are present at a particular stage of development
most are an inactive form (inhibited) and are activated by hormones/ growth factors
Operon: section of DNA that contains a cluster of genes that are all transcribed together as well as control elements and a regulatory gene. this is more common in prokaryotes
RNA polymerase cannot attach to the promoter
lactose-utilisation genes make enzymes
how does the lac operon control protein production when lactose is present?
it controls regulatory genes, elements and structural genes. when lactose is present, the regulatory gene produces the pro FINISH THIS
turning genes off:
transcription factor is coded (its a protein and active repressor)
transcription factor binds to the promoter and stops transcription
RNA polymerase cannot attach to the promoter
no gene transcription
turning genes on:
mRNA codes a protein
when lactose is present, it binds to the protein and it is now an inactive repressor
RNA polymerase binds to the promoter and codes for the enzyme
