Cellular Control Flashcards
Mutation
Random change to the structure or quantity of DNA
-gene or chromosome mutation
gene mutation
Change to one or more bases
-change to order of bases
-can happen during DNA replication
Chromosome mutation
Polyploidy- change in whole set
Non disjunction- when homologous pairs don’t separate
Chemicals as mutagens
Tar in tobacco smoke
Point mutations
Substitution of one base pair
Indel mutations
One or more nucleotides are inserted of deleted
cause frame shift
code for different amino acids
Nonsense
Result in STOP codon
Polypeptide chain becomes truncated
Missense
Different amino acid formed
-altering shape
-prevents it carrying out its function
will change all polypeptide sequence
Silent
No effect as code may still code for same amino acid
-polypeptide still carries out normal function
Lac operon
length of DNA made from structural genes and control sites
Structural gene –> codes for protein
Control sites -> operator and promoter region of DNA
how can mRNA be modified post translation
Activation of proteins like adrenaline
when adrenaline is activated it causes the synthesis of cAMP from ATP
causes further enzyme reactions which activates the protein
how can mRNA be modified after transcription
introns spliced out
primary mRNA modified to mature mRNA
to prepare for translation
promotor region
binding site for RNA polymerase
operator region
repressor protein binds to prevent RNA from binding to transcribe genes
beta galactosidase (Z)
hydrolyses lactose into galactose and glucose
lactose permease (Y)
protein that becomes embedded in e coli membrane
helps transport more lactose into cell
regulatory gene (I)
produces the mRNA
can limit mRNA production to stop transcription / translation of genes
if lactose present
mRNA produced
Repressor protein made
lactose binds to repressor protein
forms an inducer repressor complex
therefore moves away from operator region
RNA polymerase CAN bind
Z&Y turned on
if no lactose
mRNA transcribed at ribosome (makes repressor)
repressor protein binds to operator region (covering P)
RNA polymerase CANNOT bind to promotor
Z&Y turned off
Transcription factors
In eukaryotic cells
proteins or short RNA which bind to promotor regions of DNA
AID or INHIBIT the attachment of RNA polymerase
exons
coding regions
introns
non-coding regions
can be spliced out
mutations in introns do not make a difference
Homeobox genes
genes whose activity switches a whole set of other genes on or off
controls an organisms body plan
code for production of transcription factors
(regulatory gene) in animals plants and fungi
CAN BE FATAL
homeobox acting as tumor suppressor cells
they prevent cells from dividing too rapidly
mutations in hox group
limb malformation
mutations in pax
eye deformations
what do homeobox genes do
make sure body plan is correct as mutations in this could be lethal
if head grows in the wrong place the organism cannot function properly
Very important
Been very little change in homeobox genes
Apoptosis
programmed cell death
also helps body plan as cells can be killed off to form body parts
eg tadpoles tail is removed through apoptosis to form frog
can keep cell division constant and can prevent cancers forming
Process of apoptosis
Enzyme breaks cytoskeleton
Cytoplasm become dense with tightly packed organelles
Cell surface membrane changes (blebs form)
Chromatin condenses, nuclear envelope breaks (DNA breaks into fragments
Cell breaks into vesicles digested by phagocycotic cells
how is development caused by homeobox genes
They code for transcription factors that activate genes when needed for development of body plan in eg zygote
Their sequences are similar in plants and animals
how is development caused by mitosis
Primary mechanism of growth
genes regulating growth respond to stimuli internal or external to control growth
how is gene expression regulated at transcription level
Transcription factors these are genes that can either inhibit or initiate transcription of genes so that only certain parts of DNA are expressed
how is gene expression regulated at post transcriptional level
introns spliced out produce mature mRNA ready for translation
