BIOL SCI 215 Lecture Notes - Lecture 4: Okazaki Fragments, Primase, S Phase
28 Jun 2018
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DNA Structure and Replication
Morgan’s model: genes are like beads on a string
oGene sometimes called a “locus” (plural - loci)
oA location on a chromosome and its a particular stretch of DNA sequence
Griffith’s experiments: Something can transform R cells into S cells
oPossible Inheritance
oDNA was the inheritance molecule / transforming agent
Hershey- Chase experiment: virus bacteriophage DNA not protein is transferred into
infected cell
oDifferentiate with radio-labeled atoms/isotopes
oShows that radiolabeled DNA was transferred not proteins
Chargaff’s rule - for each organism, A and T are in equal abundance as well as C
and G are in equal abundance
Crystallography - DNA crystallized into lattices and a diffraction pattern is produced in
the X ray after they hit the sample, showing the 3D arrangement of atoms
oSuggests that DNA is a double helix through the diffraction pattern
Overall structure of DNA (Deoxyribonucleic acid)
oSugar phosphate backbone (outer part of DNA)
Don’t need to know major and minor grooves
Molecule adopts helix because of interaction between successive
base pairs
oDNA is a polymer composed of nucleotide monomers (nucleotide bases)
Deoxy refers to lack of -OH hydroxyl group at 2’ position
Hydrogen bonding in DNA composed of Purines (A,G 2 rings) and
Pyrimidines (C,T, U 1 ring), T and U are almost similar
Deoxynucleotide Triphosphate (NEED TO KNOW), OH group at 3’
position
3 Phosphates connected to a 5-member carbon ring with a
base
Structure of four DNA nucleotides (Just need to know that it is a
nucleotide)
oDetailed structure of DNA
Purine and Pyrimidines are able to hydrogen bond to each other
Each Phosphate carries a negative charge and thus DNA is negatively
charged
Each strand has a directionality
Important features:
Phosphate backbone is negatively charged
Middle of double helix is hydrophobic
Two strands held together by hydrogen bonding
Anti-parallel notice 5’ - 3’ polarity on the strands
Complementary strand of DNA
Switch base pairs
oMelting temperature
Heat will separate strands of DNA
CG base pairs have 3 hydrogen bonds, AT has two hydrogen
bonds
Longer strand = more hydrogen bonds
oThree models for DNA replication
Semi- conservative
Labeling experiment shows “semi-conservative” replication
occurs
Conservative
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Morgan"s model: genes are like beads on a string: gene sometimes called a locus (plural - loci, a location on a chromosome and its a particular stretch of dna sequence. Griffith"s experiments: something can transform r cells into s cells: possible inheritance, dna was the inheritance molecule / transforming agent. Hershey- chase experiment: virus bacteriophage dna not protein is transferred into infected cell: differentiate with radio-labeled atoms/isotopes, shows that radiolabeled dna was transferred not proteins. Chargaff"s rule - for each organism, a and t are in equal abundance as well as c and g are in equal abundance. Overall structure of dna (deoxyribonucleic acid: sugar phosphate backbone (outer part of dna) Don"t need to know major and minor grooves. Molecule adopts helix because of interaction between successive base pairs: dna is a polymer composed of nucleotide monomers (nucleotide bases) Deoxy refers to lack of -oh hydroxyl group at 2" position.
