Gene regulation Flashcards
constitutive genes:
genes expressed all the time
regulated genes:
genes only expressed when needed
housekeeping proteins: and eg
- proteins which are always needed
- ribosomal proteins
how does a cell regulate production of proteins:
- feedback inhibition
- gene regulation
prokaryotes: feedback inhibition
- activity of first enzyme in pathway stoped by end product
prokaryotes: gene regulation
- gene coding for enzymes in metabolic pathway are controlled
prokaryotes: operon general features
- prokaryote genes often arranged in operons
- same genes under control of single promotor
- all necessary proteins produced at same time in response to same stimulus
operons: list parts
- operator
- promoter
- genes that they control
operons: operator
- regulatory ‘switch’
- segment of DNA positioned within the promotor
operons: switched off by
protein repressor
operons: repressor
- prevents gene transcription by binding to operator
- blocking RNA polymerase
operons: what codes for repressor protein
- by regulatory gene
- located elsewhere in genome (co-repressor is tryptophan)
repressible operons:
- usually on
- binding a repressor to operator will shit off transcription
repressible enzymes: function when
- in anabolic (creating metabolites) pathways
- synthesis repressed by high levels of end product
- eg. tryptophan synthesis
inducible operons:
- usually off
- inducer inactivates repressor to turn on transcription
inducible enzymes: function when
- in catabolic (breaking down metabolic) pathways
- synthesis induced by chemical signal
- eg. lactose
lactose: general features
- major sugar of milk
- uncommon nutrient for bacteria
- enzymes for lactose metabolism usually not expressed (conserve energy)
lactose: energy for cells
- cells use glucose for energy
- lactose: disaccharide of glucose and galactose
lac operon: list enzymes involved
- permease
- b-galactosidase
- transacetylase
lac operon: permease
- allows lactose to enter bacterial cell
lac operon: b-galactosidase
- breaks down lactose to glucose and galactose
lac operon: transacetylase
unknown function, assists lactose breakdown
lac operon: lac I
- control gene
- encodes lac repressor protein
- when bound to DNA (operator) will prevent transcription at lac operon
lac operon: inducer
- form of lactose
- binds to repressor protein and inactivates it -> transcription of lac operon
negative control:
- both inducible and repressible operons involve negative control of genes (via repressor)
positive control:
- regulatory protein that switches transcription on
- eg. CRP activity in lac operon
when is CRP inactive:
- if glucose and lactose is present
- reduced expression of lac operon
when is CRP active:
- lactose present
- no glucose
- high levels of lac operon transcription
eukaryotes: gene transcription
- multiple control elements
- segments of noncoding DNA act as binding sites for transcription factors (help regulate transcription)
eukaryotes: what are critical to precise regulation of gene expression in different cell types
- control elements
- transcription factors
proximal control elements:
- located close to promotor
distal control elements:
- groupings of enhancers
- may be far away from a gene or even located in an intron
where do transcription factors bind:
- to TATA box within promoter/ other proteins/ transcription factors or RNA polymerase
when does complete transcription occur:
- when complete transcription initiation complex is assembled
- eg. RNA polymerase and transcription factors
how can some transcription factors also function as:
repressors
an enhancer has:
- 10 control elements
control element:
- binds 1-2 specific transcription factors
combo of control elements important:
- in transcription regulation
coordinated transcription: features
- unlike genes of prokaryotic operon, co-expressed eukaryotic genes have promoter and control elements
- genes can be scattered over different chromosomes but each has same combo of control elements
copies of activators recognise specific control elements and promote:
simultaneous transcription of the genes
post-transcriptional regulation:
- mRNA only codes for a protein-> the protein that carries out the function
after transcription we can have:
- alternative RNA splicing
- block translation with regulatory proteins that prevent attachment of mRNA to ribosome
- regulation of post-translational modification of protein
cell differentiation:
- process of cells becoming specialised in structure and function
stem cell:
- relatively unspecialised cell that can reproduce itself indefinitely and differentiate into specialised cells of one or more types
embryonic stem cell:
- isolated from early embryo which are able to differentiate into all cell types
do adults have stem cells:
- yes
- replace non-reproducing cells as needed
totipotent stem cells:
- obtained from early embryos, spores, plant calluses
- give rise to complete individual
pluripotent stem cells:
- give rise to many different cell types
- cannot produce entire individual
multipotent stem cell:
- gives rise to different cell types within tissues
induces pluripotent stem cells (iPS):
- potentially used to treat repair of damaged tissue in adults
- using skin cells, reprogramming them
proto-oncogene:
normal version of a gene
oncogene:
cancer causing gene
