Lecture 2 & 3 DNA intro Flashcards
what are DNA 3 functions?
(SRM)
1. store info
2. replicated
3. mutates
what is the central dogma ?
DNA (TRANSCRIPTON
RNA (REPLICATION AND TRANSLATION)
Protein
what initiates gene expression
transfer of info
what is a semi conservative model?
same 1 double dna strand converts to
1. 2 dna both with a new dna strand and an old dna strand
2. after replication the previous 2 dna that have old and new along with 2 dna that complete have two new strands together
what is a conservative model ?
same 1 double dna strand
1. 2 dna one with a dna with both original stands and the second dna with both completely new dna strands
2. after replication 4 dna ( 3 all new) (1 is the original )
what is the dispersive model
same 1 double dna strand
1. 2 dna stands that are MIXED with both old and new
2. after replication 4 more dna stand that both strands are mixed with old and new
what did meselson and stahl do in 1958
meselson and stahl first grew ecoli in heavy nitrogen (15n) and transferred it to (14n) medium nitrogen and put it in a cetrifuge tube and the cetrifuge seperated it with the concetration of cscl, heavy dna at bottom
medium dna in middle
light dna at top
what did meselson and stahl prove ?
dna replication is semi conservative
why are 5 reasons mutation in dna important
1.to alterate protein or rna
2. evolution
3.form new allees
4. no product (protein or rna)
5.altered regulation of a product
what are the 4 things a nucleic acid structure is comprised of
?
1.nitrogenous base
2. ribose sugar
3. phosphate group
4.nucleoside(tides)
what are the 5 nitrogenous bases ? and which is one is for rna only and dna only
adenine
guannine
cytosine
thymine (DNA)
uracil (rna)
what is the difference of the ribose sugars between dna and rna ?
dna has one alcohol groupd
rna has 2 alcohol groups
what is a polynucleotide chain and how does it link ?
is multiple nucleitide and is linked via a phospherdiaster bond
how is nucleic acids read
5’ end to 3’end
what did watson and crick do
figure out the 3d structure of dna
what is chargaff rule ?
number of A=T
Number of G=C
what is B-dna
dna that has a major and minor goove and complete one turn in 10.5 base pairs
what are three things major and minor grooves are good for ?
1.binding sites for different factors
2. recognizing specific nucleotides sequences on dna
3. has a distrubution of acceptors and donors
what are the 5 forces that help form the double helix ?
1.phosphate back bone
2. stacking interaction (vanderwalls)
3. hydrophobic interactions
4. ionic interactions
5. hydrogen bonding
what are the three forms of dna ? which is the only one that is left handed
A
B
Z - left handed
what is the rise/base pair along the helix axis for (A) for b-form
0.34 nm
what is the mean bp/turns for b-form
10
what is the diameter for b-form ?
2nm(nano meteres)
what are 5 things that denature dna
1.heat
2. low ionic strength
3. agents that influence hydrogen bonds
4. agents that enhance solubility of hydrophobic substances
5.high pH
how can you monitor dna denature
via absorbance
how does an absorbtion spectroo.. work ?
when dna is is double stranded absorption is low , which single stranded it increases
what is hypochomic
when dna is still double standed and absortion is low
what is hyper chromoic
when dna is single stranded and absorption is high
in absorption sepc.. what is temperatue (tm)/ based on ?
the GC content , more gc conetent more temperatuve needed
