cellular control🐛 Flashcards
effect of insertion mutation
- reading frame shifts by one base (frameshift)
- alters triplet codes for amino acids
- amino acid sequence from point of frameshift will be different
in the lac operon describe how Z and Y genes are controlled in the absence of lactose
- regulatory gene produces repressor protein
- repressor protein binds to operator
- RNA polymerase cannot move to promoter
- genes Z and Y not expressed
what is the advantage of the lac operon being controlled by presence of lactose
- organism saved energy by only producing lactase in presence of lactose
- lactase produces when only lactose is available as a respiratory substrate
what is a homeobox gene
- homeotic or regulatory gene that contains a homeobox sequence
- controls development of body plan
how does a homeobox gene carry out its function
- homeobox gene codes for transcription factor
- TF binds to DNA with homeodomain
- TF controls expression of other genes by switiching them on and off
what does highly conserved across species mean
homeobox genes in all species have very similar gene sequence and are located in the same positions
suggest why homeobox genes have not really been changed by mutation
- mutation in homeobox genes likely to affect body plan or affect many other genes
- likely to be selected against
outline apoptosis
- enzymes break down cytoskeleton
- nucleus breaks down
- bulges/blebs appear in plasma membrane
- cell breaks down into vesicles
describe plant cloning
- cutting from parent plant
- dip in plant hormones
- put into pot where it grows into genetically identical plant
advantages of plant cloning
- greater yield as all plants are desirable
- pest resistant so no pesticide needed
- faster to produce
disadvantages of plant cloning
- less able to adapt to climate change
- more susceptible to same disease
- decreases biodiversity
types of substitution mutation
- silent
- missense (changes one amino acid)
- nonsense (causes premature stop codon)
what are the 3 regulatory mechanisms
- transcriptional level
- post transcriptional level
- post translational level
what are regulatory mechanisms for
- not all genes expressed in all cells
- not all genes expressed all the time
- regulatory mechanisms ensure correct genes are expressed
what is an operon
- group of genes controlled by same promoter
- under same regulatory mechanism
- transcribed together
function of promoter
RNA polymerase binds to begin transcription
what do the genes in the lac operon code for
lacZ= lactase lacY= permease lacA= transacetylase
how to find out what genes are being expressed in a cell
analyse RNA is present as this shows which genes are transcribed
where do transcription factors bind
promoter
how are gene expressions regulated post translation
- protein modified by golgi apparatus
- activation by cAMP
- binding of cAMP alters shape of protein
post transcription regulation
introns removed from mRNA by splicing to produce mature mRNA
what are homeobox genes
- regulatory genes
- controls development of body plan
- by regulating mitosis and apoptosis
- code for homeodomain
what is homeodomain
- transcription factor
- binds to DNA to regulate transcription
what is a hox gene
-homeobox gene in animals
what organisms have homeobox genes
highly conserved in plants, animals, fungi
how does apoptosis control growth
cells produced earlier in development may no longer be needed
what do tumour suppressor genes do
reduce cell division or stimulate apoptosis
what do genes that control the cell cycle and apoptosis respond to
- internal stimuli: irreparable DNA damage, RNA decay, biochemical changes, can initiate apoptosis in stressed cells
- external stimuli: presence of signalling molecules eg cytokines hormones growth factors, pathogens pollutants and UV may damage cells faster than they are replaced
explain how failure of the control mechanism by hox gene could lead to deformities
- transcription factor not activated
- gene expressed which should not have been
- molecules signalling apoptosis not produced
- if apoptosis does not occur, deformities can form
explain how a mutation could alter a protein so that it no longer performs its function
- if frame shift then all triplets downstream will be different
- different tertiary structure so different shape
where do transcription factors bind
promoter
how is it possible for a mutation to have no effect on protein
- genetic code is degenerate so many combinations of triplets may code for same amino acid
- amino acid sequence not altered
- shape not altered
