6.1 Gene Expression Flashcards
what are genes that code for enzymes constantly required for respiration called?
housekeeping genes
what are genes that code for protein based hormones only required at certain times called?
tissue specific genes
how is expression of genes regulated?
switching genes on and off
increasing or decreasing the rate of product synthesis
bacteria respond to changes in environment by expressing genes when?
when products are required
what is gene regulation in multicellular organisms needed for?
cell specialisation
what levels are genes regulated at?
transcriptional
post transcriptional
translation
post translational
at transcriptional level what can happen to genes?
they can be turned on or off
at post transcriptional level what happens to mRNA?
it is modified regulating transcription and the types of protein produced
at translational level, what can happen to translation?
it can be stopped or started
at post translational level what can happen to proteins?
they can be modified after synthesis changing their functions
(transcriptional control) what are the different types of transcriptional control?
chromatin remodelling
histone modification
lac operon
cyclic AMP
(transcriptional control) chromatin remodelling by histone modification is often called what?
epigenetics
(transcriptional control) what is chromatin?
DNA wound around histones in eukaryotic cells
(transcriptional control) what is heterochromatin?
tightly wound DNA visible during cell division
(transcriptional control) what is euchromatin?
loosely wound DNA during interphase so DNA can be replicated
(transcriptional control) why does DNA coil around histones?
histones are positively charged
DNA is negatively charged
(transcriptional control) what is acetylation and what effect does it have?
addition of acetyl groups
reduces positive charge of histones
DNA coils less tightly allowing genes to be transcribed
(transcriptional control) what is phosphorylation and what effect does it have?
addition of phosphate
reduces positive charge of histones
DNA coils less tightly allowing genes to be transcribed
(transcriptional control) what is methylation and what effect does it have?
addition of methyl group
makes histones more hydrophobic
DNA binds more tightly
(transcriptional control) what is an operon?
group of genes under control of same regulatory mechanism expressed at the same time
(transcriptional control) why is an operon efficient?
way of saving resources
if certain gene products aren’t needed all genes switch off
(transcriptional control) lac operon - what is a regulatory gene?
located near the operon
codes for a repressor protein
(transcriptional control) lac operon - what is the repressor protein?
binds to operator preventing RNA polymerase binding and transcribing structural genes in absence of lactose
(transcriptional control) lac operon - what is the lac operon?
group of 3 genes, lacZ, lacY and lacA involved in metabolism of lactose
code for 3 enzymes
(transcriptional control) when lactose is present what does it do?
binds to the repressor protein causing it to change shape so it cant bind to the operator
(transcriptional control) when lactose is present what can RNA polymerase do?
bind to the promoter
transcribing the genes so the enzymes can be synthesised
(transcriptional control) why is the lac operon described as being leaky?
it is still transcribed to a limited extent even in the absence of lactose
without lactose permease (one of the enzymes produced) lactose would never be able to enter
(transcriptional control) what is epigenetics?
heritable changes to gene expression in eukaryotic cells (genes switched on/off which can affect the phenotype of the cell)
(transcriptional control) epigenetics - how can genes be silenced?
DNA methylation & histone modification
(transcriptional control) epigenetics - what does the enzyme histone deacetylase remove?
acetyl groups from histones
causing gene silencing making the DNA histone complex more tightly packed
(transcriptional control) epigenetics - for a epigenetic factor to be passed between generations where must it be found?
gametes
(transcriptional control) epigenetics - what is a factor that affects development of bees?
all bee larvae are identical but if fed royal jelly with royalactin they will become queens with reduced levels of DNA methylation
(transcriptional control) epigenetics- give an example of genetic imprinting (genetic factor that can be passed on)?
Angelman syndrome maternal copies are missing or inactive and paternal copies are silenced resulting in learning difficulties and growth abnormalities
