6.1.1 cellular control Flashcards
what is substitution mutation
- one base is swapped for another
- silent or missense
what is insertion mutation
- an extra base added into AA sequence
- causes a frameshift where the reading of the AA sequence is changed
what is deletion mutation
- a base is removed from the DNA sequence
- frameshift
silent vs missense vs nonsense mutation
silent - no change in protein (degenerate)
- missense - changes one amino acid
- nonsense - stop codon - shorter- non-functional protein
what do both insertion and deletion do
- frameshift mutation
- alter the AA sequence of the protein
- can no longer function
what is the beneficial impact of mutations
- it can give an organism and advantage
- e.g antibiotic resistance
what is the neutral impact of mutations
- no effect on protein function
what is the harmful impact of mutations
- can cause genetic disorders or cancer
transcriptional vs post- transcriptional level vs post-translational level
- transcriptional -regulates whether mRNA is made
- post-transcriptional - modifies mRNA before translation
- post-translational - activates proteins after translation
transcriptional control in prokaryotes
- No Lactose → Genes OFF
- A repressor protein binds to the operator, blocking the promoter and RNA polymerase cant transcribe the structural genes.
- Lactose Present → Genes ON
- Lactose binds to the repressor, changing its shape so it detaches.
- RNA polymerase can now transcribe the genes needed to digest lactose.
- cAMP and CRP upregulate the activity of RNA polymerase increasing the efficiency
translational control in eukaryotes
switching on or off translation
off:
- degrade mRNA - no more = no translation
- inhibitory proteins will bind to mRNA, can’t bind to ribosome
on:
- activate initiation factors allow mRNA will bind to ribosome
- done by phosphorylation by protein kinases also activated by cAMP
post-translational control in eukaryotes
modify polypeptides to make proteins of specific functions
- add a non-protein group to it e.g glycoprotein for cell signalling
- modify amino acids bond e.g cha AA to cystine to make disulfide bridges
- change the protein folding (3’ or 4’)
- modification by cAMP e.g cAMP and CRP which bind to RNA polymerase and upregulate its activity OR activates protein kinases or other enzymes
homeobox genes in the control of body plan development
- highly conserved - similar in plants, animals and fungi
- Homeodomain sequence - folds and binds to specific parts of DNA - acts as a transcriptional factor
hox genes in the control of body plan development
- found in animals
- arranged in clusters - expressed in order of head to tail
what is apoptosis
- programed cell death
- removes damaged or unneeded cells
example of when apoptosis is used
- to stop webbing between fingers in embryo development
where do signals for apoptosis come from
- inside - DNA damage
- outside - stress signals from other cells
imbalance of apoptosis
- too little = cancer
- too much = neurodivergent diseases - Alzheimer’s
what is a gene mutation
change in the sequence of DNA which alters the protein function and position
alternative splicing example
- same gene can code for different forms of muscle proteins (e.g., in the heart vs. skeletal muscles)
what is an operon
a group of genes controlled by the same regulatory mechanism
what is the operator
DNA sequence where the repressor protein binds to
what is the promoter
DNA sequence where the RNA polymerase binds to
difference between structural genes and regulatory genes
- structural: proteins NOT involved in DNA regulation
- regulatory: proteins that ARE involved in DNA regulation
what does each structural gene make
- Lac Z: B-galactosidase
- Lac Y: Lactose permease
- Lac A: Lactose transacetylase
transcriptional control in eukaryotes
heterochromatin (tightly wound DNA in cell division)
- gene is inaccessbile
- RNA polymerase cannot bind
- acetylation/phosphorylation to decrease the +ve charge of histones turning it into Euchormatin
euchromatin (loosley wound DNA in interphase)
- gene is accessible
- RNA polymerase can bind
- turn it into heterochromatin by methylation which increases the hydrophobic nature of histones
post-transcriptional control in eukaryotes
- pre-mRNA to mRNA by splicing
- remove introns keep exons
- in order to prevent the mRNA from degrading:
- add a cap (modfied nucleotide) and a tail of adenine
- the mature mRNA can create different versions because exons can combine in different ways to make different proteins (alternative splicing)
what are point mutations
affects only one base
- substitution, deletion or insertion
