Exam 1 Notes (2) - Lecture Notes - Genetics [DNA Structure]...

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Lecture Notes - Genetics [DNA Structure] (The substance of heredity) - Experiment 1: Frederick Griffith infects mice with Streptococcus pneumonia (1928) - Uses two strains. The Smooth Strain(S-Strain) and the Rough Strain(R-Strain) - S-Strain (Living): - When injected into mice, mice died - A raging infection caused the death - Griffith took blood samples from the mice, and was able to isolate colonies of the smooth strain in spread on a Petri plate - These S-Strains secrete a polysaccharide capsule coat buffering the infection of bacteria - R-Strain (Living): - When injected into mice, mice survived - The infection was managed, and the bacteria was killed - Could not isolate any living bacteria from the mice's blood - These R-Strains do not form a polysaccharide coat - S-Strain (Dead): - Griffith boiled and heat killed the S-Strain bacteria first, and then injected it into the mice. The mice survived - Could not isolate any living bacteria from the mice's blood - R-Strain (Living) & S-Strain (Dead): - Mixed living R-Strains and heat-killed S-Strains, then injected it into the mice. The mice died - Was able to isolate S-Strain bacteria from the mice's blood afterwards - How were S-Strain bacteria isolated from the dead S-Strain cells? - Because R-Strain bacteria cannot mutate to S-Strain bacteria, the interpretation of this was that something from the dead S- Strain bacteria was transforming the R-Strain bacteria into S- Strain bacteria - In terms of reproduction, R-Strain cells reproduced into S- Strain cells, but only in the presence of S-Strain cells - Griffith called this process transformation, and whatever it was causing this, the transforming principle - Something in S-Strain cells transformed/changed R-Strain cells into S- Strain cells - Trait that passes from parent to offspring - Griffith sees this as Mendel's genetics - This experiment showed that some genetic material from the dead bacteria transferred to the living bacteria and provided them with a new trait - However, Griffith did not know what the transforming substance was - Experiment 2: Avery, Macleod, & McCarthy isolate & characterize the transforming principle (1940's) - These three men knew that Griffith's observations could be used as part of an experimental strategy to identify the genetic material. - At the time of these experiments, researchers already knew that DNA, RNA, proteins and carbohydrates were major constituents of living cells - To see if any of these were the genetic material, these men ran a series of tests - (Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA)) - Nucleotide - Nitrogenous base
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Lecture Notes - Genetics - Ribose vs. Deoxyribose - Phosphate - Numbering carbons on sugars - Nucleotide nomenclature - Phosphodiester bond (Watson and Crick and the double helix) - Chargaff's rule - Analyzed a lot of DNA - Proportions were very consistent w/in species - A=T, G=C - Franklin - She performed X-Ray diffraction on DNA by shooting an X-Ray beam at a crystal - Finds a spiral or helix shape. Took dimensional measurements of the helix
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Exam 1 Notes (2) - Lecture Notes - Genetics [DNA Structure]...

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