DNA Structure Review

The Griffith Experiment: Hereditary Information Can Pass Between Organisms Frederick Griffith Non-pathogenic S. pneumoniae was transformed by dead pathogenic S. pneumoniae. Information specifiying the virulent surface protein had been delivered to the safe live form.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Mice die; their blood contains live pathogenic strain of S. pneumoniae Mixture of heat-killed pathogenic and live nonpathogenic strains of S. pneumoniae + Heat-killed pathogenic strain of S. pneumoniae Live pathogenic strain of S. pneumoniae Live nonpathogenic strain of S. pneumoniae Polysaccharide coat Mice liveMice die (1)(3)(4) Mice live (2) Griffith Experiment

Avery, MacLeod, McCarty The Tranforming Agent is DNA Repeated Griffith’s Experiments to substantiate. When protein, carbohydrate, and fat were removed, the bacteria were still transformed When nucleic acid removed, no transformation

Hershey and Chase - (p. 283) Bacteriophage: virus with a simple nucleic acid and a protein coat. Tracked DNA by marking phosphorous with 32 P (only DNA contains phosphorous) Tracked protein by marking sulfur with 35 S (only protein contains sulfer). Found that it was the DNA, marked with 32 P, that was injected into the bacteria that caused disease.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Protein coat labeled with 35 S DNA labeled with 32 P Bacteriophages infect bacterial cells. T2 bacteriophages are labeled with radioactive isotopes. Bacterial cells are agitated to remove protein coats. 35 S radioactivity found in the medium 32 P radioactivity found in the bacterial cells

Nucleic Acid Structure Both DNA and RNA are formed of nucleotides joined together in series. Each nucleotide is composed of a five- carbon sugar, a phosphate group, and a nitrogen-containing base. (p. 309)

Chargaff's Rule - there are always equal proportions of purines and pyrimidines. (p ) A-T G-C Pure AGgie (purines are A & G) Purines have a double ring structure. Pyrimidines have a single ring structure. Single always pairs with double..

How to number the sugar carbons.. -Base attached to 1’ phosphate attached to 5’. This comes up when we talk about replication, transcription, and translation. (We read from 5’ to 3’) Phosphodiester bond between nucleotides.

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DNA strands are antiparallel

The Meselson-Stahl Experiment: DNA Replication Is Semiconservative Matthew Meselson and Franklin Stahl demonstrated that DNA replication is semiconservative because each strand of the original duplex becomes one of the two strands in each new duplex. (p. 312) –Also figured this out by using isotopes, this time 15 N.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4. The DNA was suspended in a cesium chloride solution. Centrifugation 1234 Control group (unlabeled DNA) Labeled parent DNA (both strands heavy) F 1 generation DNA (one heavy/light hybrid molecule) F 2 generation DNA (one unlabeled molecule, one heavy/light hybrid molecule)

The Replication Process Replication of E. coli begins at a specific origin, proceeds bidirectionally, and ends at a specific terminus. (p. 290) OriC is beginning point. Contains many A-T pairs, which are double bonded, easy to open. Leading and lagging strand. One side is synthesized continuously, but the other limited to short segments (Okizaki fragments).

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. DNA polymerase III DNA double helix Lagging strand Primer Okazaki fragment Leading strand

DNA primase -creates a short RNA primer complementary to a DNA template; DNA helicase, which unwinds the helix DNA polymerase, which then synthesizes new DNA by adding nucleotides to the growing strands; and DNA ligase, which creates phosphodiester bonds between adjacent Okazaki fragments. (pp ) Each of these has a name that gives away its job.

Replication fork- Open area of DNA where replication takes place. Replication can be divided into three stages: initiation, elongation, and termination. (p ) Initiation- there are two OriC’s, one on each strand.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Leading strand Lagging strand DNA ligase DNA polymerase I Okazaki fragment RNA primer First subunit of DNA polymerase III Single-strand binding proteins Second subunit of DNA polymerase III Primase Helicase Parental DNA helix

DNA REPLICATION DNA Replication is directional. Synthesis of DNA and RNA occurs in the 5’ to 3’ direction. What part of the cell cycle is replication?

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. OH CH 2 O PO 4 Base