5a slides Flashcards
(47 cards)
what do prokaryotes and eukaryotes do in response to cellular and environmental cues
regulate gene expression
in multicellular eukaryotes what does gene expression regulate
development and is responsible for differentiation of cell types
promoter
specific nucleotide sequence of a gene that binds RNA polymerase
what binds to a specific DNA sequence called a promoter
RNA polymerase
where does the promoter position the RNA polymerase and in what direction does it point the enzyme
at the start of the gene and points the enzyme in the right direction to transcribe a given gene
what do proteins recognize and bind to
discrete sites
what is the most likely consequence of the DNA binding site for a particular protein is mutated
mutations can enhance and decrease binding affinity between proteins and DNA
downregulation
less protein made
upregulation
more protein made
domains of proteins that bind DNA in a nucleotide fit in where
in the groove of the doubke standard helix where it can form non covalent bonds with the correct base pairs
how does bacteria respond to environmental changes
by regulating gene expression
Natural selection has favored bacteria that produce only the gene products needed to live in a particular environment. Why?
a cell can regulate the production of enzymes by gene regulation
what is the operon a mechanism for
the coordinate control of multiple genes that affect a single bacterial trait
operon
the entire stretch of DNA that incldues the oeprator, the promoter, and all the genes they control
what does it mean when you see a word before operon in italic
that it is a gene
what does the trp operon code for
all the enzymes required to synthesize the amino acid, tryptophan
what is the switch in a segment of DNA called, what does it often overlap with
an operator and often overlaps the promoter region
what are encoded within a single mRNA
multiple polypeptides
what can the trp operon be switched off by
a protein repressor
what does the repressor prevent
gene transcription by binding to the operator and blocking out the RNA polyermase
what is the repressor the product of, where is it located
a seperate regulatory gene, located some distance away from the operon itself
qualites of trp present in the environment
-bacterium does not need to make tryptophan
-repsenting trp operon saves energy required to synthesize the enzymes of the pathway to make trp
qualities of tryptophan absent in the environment
-bacterium needs tryptophan for synthesis of proteins
-removing repression of trp operon allows synthesis of the enzymes of the pathway to synthesize trp
what form can you find the repressor
in active or inactive form depending on the presence of other molecules
