LEC EXAM #3 CHP. 11 Flashcards
Point mutation:
Insertion or deletion of 1 or 2 bases at DNA level-> causes shift/missence in amino acid at protein level
Silent mutation:
Mutation that doesn’t effect amino acid but shifts AKA FRAMESHIFT MUTATION
BEST and WORST place for mutation on DNA codon:
Best: 3rd pos.
Worst: 1st pos.
BEST place for mutation:
In telomere or centromere because no genes
Which mutation is worse? nonsense or missense
Nonsense because makes the protein nonfunctional
Nonsense mutation example:
CCR5 DELTA 32- coreceptor HIV uses for entry -> HIV can’t enter cell-> HIV resistant
NONSENSE mutation:
Causes early stop codon-> protein terminates early-> nonfunctional
Ames test:
Test compounds to see if mutagenic/carcinogenic
Revertants:
Mutagen compound that mutates strain from his- into his+ that grows on media lacking histidine
How does Ames test work? (6)
- Genetically modified strain of salmonella that no longer has a functional histidine gene
- Add rat liver extract
- Grow strain in media containing histidine
- In another tube, add rat liver extract + mutagen
- Plate on media that does not contain histidine
- If able to grow on media lacking histine-> mutated his- to his+
What did that compound do to make the revertants?
Caused mutations that causes it to move back to his+
Compound is:
Mutagenic which makes it carcinogenic
Conjugation:
Form of horizontal gene transfer that uses a pilus to transfer the plasmid
Cell with plasmid:
F+ cell
Cell without plasmid:
F- cell
What allows transfer of plasmid DNA from F+ cell to the F- cell?
Pilus
Result of transfer of plasmid DNA from F+ to F- cell?
2 new double stranded plasmids
Operons:
Set of genes for a particular pathway that results in an enzyme
In the absence of tryptophan:
the TRP repressor dissociates from the operator and RNA synthesis proceeds
In the presence of tryptophan:
the TRP repressor binds the operator and RNA synthesis is blocked
T or F
Repressor protein is always present inside the cell.
True
What happens when TRP binds to the repressor?
Causes a conformational change in the repressor when it that allows it to bind to the operator
Repressible operon:
Can be repressed/turned off if it comes in contact with TRP, but normally it’s always on until you turn it off
Lac operon:
Inducible operon that stays turned OFF until coming in contact with lactose
When lactose binds to repressor:
Conformational change which doesn’t allow it to bind to the operon
Cyclic AMP is made from:
Low levels of glucose and high levels of lactose
cAMP-clyclic AMP:
Works in the presence of low ATP and binds to CAP protein
cAMP + cap complex:
Makes RNA polymerase bind to promoter when we’ve used up glucose in the presence of low ATP
cAMP + cap complex is in ________ cells only:
Prokaryotic
Missence mutation:
Results in an amino acid substitution (similar to nonsense mutation)
UV light causes:
Covalent bonds between nitrogenous bases-> changes Thymine base to one big mass and therefore cannot bind
X-rays cause:
Double strands to break
In the absence of cAMP:
CAP does not bind the promotor-> transcription occurs at low rate
In the presence of cAMP:
CAP binds to promotor and increases RNA polymerase activity
In the presence of the cAMP-CAP complex:
Stimulates RNA polymerase activity and increases RNA synthesis unless repressor is bound to the operator-> RNA synthesis blocked
INSULIN:
- insert a gene of interest
- find a suitable vector (bacteriophage or plasmid) using a restriction enzyme + ligase. Human gene (insulin) + plasmid (vector)= recombinant DNA
- introduction of vector to host cell-> enters host cell-> genetically modified bacterial cell
- add resistance gene and grow in media. allowing for GMB to express human insulin
