Practice questions Flashcards
In alpha helices, how many AA residues per turn, and how many hydrogen bonds per turn?
3.6 residues per turn, # of H bonds=(total # of AA’s)-4
Where on a titration curve would you expect to find a positively charged glycine?
Low pH
Is the cytoplasm a reducing or oxidizing environment? How and what consequences does this have for protein structure?
Reducing. Several anti-oxidative enzymes are responsible for keeping the cytoplasm free of ROS. Because disulfide bonds are formed through an oxidation reaction, they are unstable in the cytoplasm
What is the sequence of events of A-beta formation?
Cleavage of APP with beta secretase, followed by gamma secretase
Define the max velocity of a Michaelis Menten reaction
Vm=k3[Etotal]
Can double stranded RNA or RNA/DNA hybrids form b-form DNA?
No, the extra hydroxyl group on RNA makes it impossible
What is satellite DNA?
Tandemly repeating, non coding DNA. Forms the main component of centromeres and heterochromatin
What is one of the mechanisms of action of p53 pertaining to the cell cycle?
It up regulates p21 and inhibits the cell cycle
What is uniparental disomy? What type of disorders are these patients at higher risk for?
When a person receives two copies from one parent and none from another.
Higher risk of imprinting disorders
True or false: nonrandom x-activation only targets abnormal x
False, in some instances, nonrandom x-inactivation can target the normal x
Do additional hydrogen bonds or Van der waals forces contribute the most to increased stability of GC pairs over AT?
Van der Waals forces
How does negative supercoiling affect the openness of DNA?
Increases openness for replication/transcription
Is apoptosis the final fate of almost all cells in the body?
No, not all cells die this way
While cells undergoing necrosis often swell and burst, apoptotic cells ______ and _____.
Shrink and condense
What does DNA polymerase alpha do?
Makes the RNA primer
What does deamination of cytosine “look” like?
top NH2 exchanged for a carbonyl
Deamination of cytosine yields:
Uracil
Deamination of 5-methylcytosine yields:
thymine
What is the significance of GC rich regions in termination (prokaryotic termination!!)?
Strong binding of GC rich regions slows the polymerase allowing a hairpin structure to form and break away from DNA (Rho-independent)
What is associated with eukaryotic transcription termination?
AAUAAA polyadenylation sequence
What does diptheria toxin do?
Modifies eE2
What does mis-splicing commonly result in?
A frameshift mutation and thus an early stop codon.
Do multiple tandem repeats of rRNA genes exist in the genome of a eukaryotic ribosome?
Yes
Do ribosomal SUBUNITS assemble in the cytoplasm?
No, but the ribosome as a whole does
Does heterodimerization (e.g. bZIP) of transcription factors greatly increase the number of potential proteins that can interact with the DNA?
Yes
What is 47 XXY?
Kleinfelter syndrome
Does RNA polymerase require a double stranded or single stranded DNA template?
double stranded
During splicing, the branch point forms a 2’-5’ phosphodiester bond with the ___
5’ end of the intron to be removed
What type of bond does aminoacyl tRNA sythetase catalyze the formation of ?
an ester bond (between aa and tRNA)
What are the components of SRP?
Has a protein and RNA component
What determines the strength of the Zn finger protein interaction with DNA?
Multiple adjacent fingers that interact with continuous stretches of DNA
HCV RNA induces an interferon response that is regulated by___
A kinase which phosphorylates eIF2, which upon phosphorylation is unable to initiate transcription
