BIOL 310: Chapter 10
26 Cards in this Set
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characteristic of genetic material (4)
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1) replication
2) storage of info
3) expression of info
4) variation by mutation
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tetranucleotide hypothesis
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-Levine
- claimed identical groups of 4 nucleotides repeated over and over were building blocks
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serotypes
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- differing strains of Diplococcus.
- defined by presence/type of polysaccaride capsule
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Hershey-Chase expt
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- DNA labeled with 32P and protein labeled with 35S
- identified that DNA was material inserted into bacterial host by phages
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absorption spectrum
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- DNA absorbed at 260nm
- proteins absorbed at 280nm
- UV light mutation frequency peak occurs at 260nm
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tobacco mosaic virus
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- RNA virus
- when hybrid virus of one strain of protein coat (HR) and one strain of RNA (TMV), offspring exhibited viral coat proteins of TMV.
- RNA was genetic material
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retroviruses
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- use RNA as template material for reverse synthesis to DNA.
- use reverse transcriptase; RNA dependent DNA pol
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nucleotide components
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1) nitrogenous base
2) pentose sugar
3) phosphate group
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ribose sugar
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has an OH group, rather than H (for DNA) at the 2' carbon
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nucleoside
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- sugar+ base, but no phosphate group
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triphosphates (NTPs)
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- adenosine triphosphate (ATP) and guanosine triphosphate (GTP)
- used for energy released from removal of terminal phosphate group
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phosphodiester bond
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-ester linkage between 5' phosphate group and 3' OH
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Chargaff and base-composition conclusions
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1) %A=%T, %G=%C
2)A+G = C+T
3) G+C does not necessarily equal A+T
- ratio varies greatly among organisms
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X-ray diffraction
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fibers of DNA are subjected to X-ray bombardment
- X-rays scatter in pattern based on molecule's atomic structure
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Watson-Crick Model
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1) 2 polynucleotide chains are coiled around a central axis, forms right handed double helix
2) 2 chains are antiparallel
3) both chains are stacked on on another, 3.4 A apart, on inside of helix
4) bases pair by hydrogen bonding
5) each complete turn of the helix is 34 A long; each t…
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Isoforms of DNA
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A-DNA: found in high-salt/dehydration conditions
- more compact (9 bases per turn)
- bases are tilted/displaced laterally
- unlikely to occur in vivo
B- DNA: aqueous, low salt conditions
- biologically significant form
Z-DNA: has left handed helix
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major classes of RNA
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rRNA (80%)
mRNA (5%)
tRNA (15%)
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Svedberg coefficient (S)
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- defines sedimentation behavior
- based on a molecule's density, mass, and shape
- higher S indicates molecules of greater molecular weight; not a direct correlation
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sedimentation behavior analysis
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load sample solution onto concentration gradient
- during centrifugation, molecules move through at different rate
- fractions are eluted, evaluated
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density gradient centrifugation
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- sample solution is added to density gradient of CsCl salt
- during centrifugation, DNA molecules of different densities will separate out until each reaches equilibrium with corresponding density of CsCl
- elute and evaluate
- GC is more dense than AT. GC content is directly proporti…
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sedimentation velocity centrifugation
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- analytical centrifuge that uses UV absorption optics to monitor migration of molecules, provides velocity (standardized to S units for Svedberg coefficient)
1) viscosity creates frictional resistance
2) force of diffusion is directed upwards
- key variables: mass and shape
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hyperchromic shift
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- increase of UV absorption of heated DNA in solution
- easy change to measure to determine DNA melting temp
- midpoint of melting profile is called melting temperature
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molecular hybridization
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- process of de/re-naturation of DNA
- single strands do not need to come from same nucleic acid source to combine to form duplex structures.
- can also occur between single strands of RNA and DNA
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DNA blotting
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- uses hybridization to probe for complementary sequences
- DNA affixed to a filter/membrane
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FISH
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- fluorescent in-situ hybridization
- miotic or interphase cells are fixed to slides and subjected to hybridization
- tagged, single stranded RNA/DNA is used to identify complementary sequences
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reassociation kinetics
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- analyzes rate of reassociation of complementary DNA strands
- results plotted as re-associated fragments vs. time (log)
- follows second order rate kinetics
- can evaluate half reaction time: varies directly with complexity of DNA= X = size of haploid genome
- areas of genome the re…
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BIOL 310: Chapter 10