cellular control Flashcards
what is a mutation?
A change in the DNA which could result in the creation of a non functioning protein as it causes a change in the base sequence of DNA.
What is a point mutation?
one base pair replaces another
What is an indel mutation?
One or more nucleotides are inserted or deleted from a length of DNA
what are the three types of point mutations?
silent, missense, nonsense
what is a silent mutation?
A change to the base triplet where the triplet still codes for the same amino acids
What is a missense mutation?
a change to the base triplet sequence that leads to a change in amino acid sequence and the tertiary structure which prevents a protein from carrying out its usual function
What is a nonsense mutation?
alters base triplet so it becomes a stop triplet which ends in a truncated protein that doesn’t function
What is a frame shift?
occurs as a result of insertions and deletions as if nucleotides base pairs are not inserted as triplets then all the triplets positioning is altered creating a frame shift which affect the primary structure of the protein
what is an operon?
the term for a group of simultaneously controlled genes that are either all expressed or not
where is the lac operon and what is its function?
usually found in coli and is a sequence of 3 genes that collectively aid with lactose digestion
What is the favoured substrate fro bacteria?
Glucose is favoured as it requires less energy to digest glucose than lactose.
What are the 3 genes within the lac operon and what do they do?
lacZ, lacY, lacA. They are involved in producing enzymes involved in lactose metabolism
What happens when glucose is absent?
lactose binds to the repressor which changes its shape and prevents it from binding yo the operator therefore lactose metabolising enzymes can be produced.
What is the process when glucose is present?
when glucose is present the repressor binds to the operator to prevent transcription and preventing the lactose metabolism enzymes being produced .
What are transcription factors?
proteins or short non coding pieces of RNA which can bind to different base sequences on DNA to begin transcription in eukaryotic cells
What are introns?
non coding regions
What are exons?
coding regions
How does cAMP activate enzymes to stimulate transcription?
- a signalling molecule binds to a receptor on plasma membrane
- activates a transmembrane protein which activates a g protein
- activates cyclase enzymes
- catalyses formation of molecules of cAMP from ATP
- cAMP activates PKA
- this causes phosphorylation of proteins which activates enzymes in the cytoplasm
- proteins enter the nucleus and act as a transcription factor
what are homeobox genes?
these are sequences of genes which create proteins that regulate the expression of genes involved in the formation of body plan
what do how genes regulate?
mitosis and apoptosis
What is the process of apoptosis?
- enzyme breaks down cell cytoskeleton
- cytoplasm becomes dense with tightly packed organelles
- cell surface membrane changes and small protrusions called blebs form
- chromatin condenses, nuclear envelope breaks and DNA breaks
- cell breaks into vesicles that are ingested in phagocytic cells.
