module 6: gene expression Flashcards
transcriptional level
transcription factors control expression- alter rate of transcription
how do transcription factors work
proteins bind to DNA and witch genes on and off by increasing or decreasing transcription rate
what factors increase transcription
activators
what factors decrease transcription
repressors
what does shape of transcription factor determine
whether it can bind or not
what is an operon
section of DNA that contains a cluster of structural genes that are transcribed together with control elements and regulatory gene
where is the lac operon
e.coli, it can respire using lactose if glucose isn’t present
what happens when lactose isn’t present
the regulatory gene produces lac repressor
lac repressor binds to operator
transcription is blocked as RNA polymerase can’t bind to promoter
what happens when lactose isn’t present
the regulatory gene produces lac repressor
lac repressor binds to operator
transcription is blocked
what happens when lactose is present
lactose binds to repressor protein and changes its shape so it can’t bind to operator
RNA polymerase can start transcription
post transcriptional level
mRNA is edited
during transcription introns and exons are copied into mRNA called primary mRNA transcripts
introns are removed by splicing and exons join forming mature mRNA
strand leaves for translation
post transcriptional level
cAMP activates proteins
controlled by molecules that bind to cell membrane to activate camp inside
cAMP changes 3D shape of proteins in cell which activates them
what controls our body plan
proteins that are coded for by hox genes
what are hox genes
have regions called homeobox genes
how do hox genes control development
homeobox sequences code for a part of the protein homeodomain
it binds to specific binding sites on DNA enabling it to work as a transcription factor
they bind at start of developmental genes to alter proteins involved in development of body plan
apoptosis
controlled cell death
how does apoptosis work
enzymes in cell break down proteins and DNA
as contents broken down cell shrinks and breaks in fragments
fragments engulfed by phagocytes and digested
mutations
change to base sequence of DNA
substitution
one or more bases swapped for another
deletion
one or more bases removed
insertion
one or more bases added
how can mutations be neutral
base changed but amino acid doesn’t in degenerate code as more than one base sequence can code for an amino acid
