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Genetics DNA structure
Terms in this set (13)
Evidence for DNA as Genetic Material
Griffith - transformation
Avery, Macleod, and McCarthy -DNA=transforming principle
Herhey & Chase - Viral DNA enters cells
Guthrie and Sinsheimer - Viral DNA codes for complete virus
Griffith's Transformation Experiments
-Two strains: IIR & IIIS
-Two differences in genotypes
R= Rough, avirulent; S= Smooth, virulent
II and III indicate different serotypes
Mice: Alone and in combination
Live and Heat killed
Live IIR & Heat-killed IIIS die.
IIR cells mutated to S?
IIR were changing into IIIS
nonliving component of IIIS cells changing genetics of IIR cells
Avery, Macleod and McCarty
Identified transforming principle as DNA.
Used purified extracts of IIIS bacteria added to live IIR; looked for loss of transformation
Heat-killed IIIS+IIR ->removed RNA and death.
Heat-killed IIIS+IIR-> Removed DNA and lived.
DNA is transforming principle.
DNA could change IIR bacteria to IIIS.
Bacteria may pick up pieces of exogenous DNA and incorporate them into their own chromosomes = TRANSFORMATION!
Hershey and Chase
Bacteriophage 2 (kills E. coli)
Which study does radioactivity end up in E. coli?
Hot protein coats = Virus planting DNA in E. coli.
Regular protein coats = E. coli w/ hot DNA
Guthrie and Sinsheimer
Redefined Hershey and Chase study.
E. coli with ruptured outer membrane.
"Naked" DNA could code for entire viruses.
Basic components of Nucleic Acids
-5 carbon sugar
Viruses: Single chromosome (Most haploid, some diploid)
-DNA or RNA
-associated histone proteins
DNA plus special proteins called histones
Organized in nucleosomes.
Euchromatin and heterochromatin
Unique sequence and repetitive sequence DNA
Needed only when a cell is about to divide.
-S phase of cell cycle prior to mitosis or meiosis.
NO OTHER TIME
Multiple origins of replication in eukaryotes.
Must add to 3' end
Phosphodiest bond "nicked" -Nuclease
Helix unwinds: Torsion stress causes H bonds between bases to break, 2 strand separate.
RNA primer needs free 3' end. RNA primase activates, removed later.
DNA polumerase III catalyzes phosphodiester bonds between new nucleotides. "Proofreads"
DNA plymerase I removes/replaces RNA primers.
DNA ligase seals Okazaki fragments.
One DNA molecule replicates to form two identical molecules
One chromosome -> Two identical chromatids.
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