Midterm 2 Flashcards
4 characteristics of genetic material
1) replicate
2) store information
3) express information
4) allow variation by mutation
what is Chargaff’s rule?
all DNA should have 1:1 ratio (base pair rule) of pyrimidine and purine bases
A = T
G = C
A+T does not necessarily equal C+G
What did Avery, Macleod, and McCarty’s transformation experiment entail?
demonstrated that DNA was the genetic material because Type R cells + Type S DNA extract + DNase resulted in no DNA being formed
Type R + Type S DNA extract + DNase ==> not transformed ==> no bacteria appeared on petri dishes
Type R + Type S DNA extract ==> transformed ==> bacteria appeared on petri dishes
Type R + Type S DNA extract + RNase ==> transformed ==> bacteria appeared on petri dishes
Type R + Type S DNA extract + protease ==> transformed ==> bacteria appeared on petri dishes
What did Hershey and Chase experiment show?
DNA, not protein, enters the bacterial cell during bacteriophage infection and directs viral reproduction
used T2 phage to infect E.coli
T2 phage protein is labeled with 35 Sulfur. DNA is labeled with 32 Phosphorus.
32P was detected in E.coli cells –> indicates that DNA is genetic material
what are the purines?
adenine
guanosine
what are the pyrimidines?
cytosine
thymine
uracil
what do nucleotides consist of?
nitrogenous base
pentose sugar
phosphate group
what is DNA nucleotide structure?
deoxyribose pentose sugar
nitrogenous base
phosphate group
what is RNA nucleotide structure?
ribose pentose sugar
nitrogenous base
phosphate group
what is difference between nucleoside and nucleotide?
nucleoside = nitrogenous base + pentose sugar
nucleotide = nitrogenous base + pentose sugar + phosphate group
DNA is a ___-handed double helix
right
the 2 DNA strands are ___
antiparallel
there are ___ base pairs per helix turn
10
what is hyper chromic shift?
absorbance of UV light by nucleic acids
ring (bases) can absorb UV light
ss nucleic acid absorbs more UV light than ds
what is hyper chromic shift used for?
determine melting temp of DNA strand
melting temp is method for estimating base composition of DNA
A-T rich DNA has lower melting temp (because only bound by 2 H-bonds while C-G has 3 H-bonds)
what is thickness of naked DNA fibers?
2 nm
what is thickness of DNA + histone (==> chromatin) fibers?
11 nm
what is thickness of solenoid fibers?
30 nm
which type of reciprocal translocation causes viable offspring? Which one causes non-viable offspring?
alternative segregation –> viable
adjacent segregation –> non-viable
describe hybrid dysgenesis
male w/ P element X female w/o P element ==> sterile progeny (hybrid dysgenesis)
male without P element X female w/ P element ==> fertile progeny
describe rho-independent termination
prokaryotic transcription termination
doesn’t depend on rho protein
RNA Pol will eventually transcribe a hairpin loop that slows down the RNA Pol –> as RNA Pol travels downstream, it encounters a uracil-rich region to which the RNA Pol is weakly bound –> this allows RNA Pol to dissociate and end transcription
describe rho-dependent termination
prokaryotic transcription termination
does depend on rho protein
RNA Pol transcribes rho recognition site (rut) in mRNA transcript –> rho protein comes and binds to rut –> RNA Pol will also transcribe a hairpin loop that slows it down –> this allows rho protein to come in contact with RNA Pol –> separates DNA and RNA –> terminates transcription
what is a lariat?
a branched intron formed during the mRNA splicing
what is a positive gene regulation?
when regulatory molecule is mutated, gene is not expressed
what is a negative gene regulation?
even when regulatory molecule is mutated, gene is expressed
what is inducible regulation?
when an agonist is present, it causes gene to be expressed
what is repressible regulation?
when an agonist is present, it causes gene to not be expressed
describe positive inducible regulation
when inducer is present, it binds to activator –> activator encourages gene expression –> gene is expressed
when inducer is absent –> activator does not bind to operator –> gene is not expressed
describe negative inducible regulation
when inducer is absent, repressor binds to operator –> gene is not expressed
when inducer is present, repressor does not bind to operator –> gene is expressed
describe positive repressible regulation
when coactivator is present –> gene is not expressed
is shine-dalgarno sequence in eukaryotes?
no; only in prokaryotes
