Biology exam 3 study guide kayla thomas

Biology exam 3 study guide kayla thomas - Biology Chapter...

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Biology Chapter 16 305-324 Pathogenic (harmful) Non-pathogenic(harmless) Transformation- a change in genotype and phenotype due to the assimilation of external DNA by a sell This was Griffiths work Studied two strains of bacterium Streptococcus pneumonia injected with s cells,r cells, heat killed s cells, heat killed s cells and living r cells He concludes the the living r bacteria had been transformed into the pathogenic s bacteria by and unkown subastance from the dead s cells that allowed the r cells to make capsules What is the transforming substance? Avery found that DNA was the transforming substance Evidence that viral DNA can program cells Studies of viruses that can infect bacteria (bacteriophages) Virus- little more than DNA enclosed by a protective coat, which is often protein To produce more a virus must infect a cell and take over the cells metabolic machinery Is protein or DNA the genetic material or is phage T2 DNA functions as the genetic material of phage T2 because…. With proteins the radioactivity remained outside the cell and with the DNA the radio activity remained inside the cell producing phages HERSHEY and CHASE up Provided powerful evidence that nucleic acids are hereditary material for viruses Erwin Chargraff DNA is a polymer of nucleotides nitrogenous base, pentose sugar deoxyribose, phosphate group Base can be Adenine, thymine, guanine, or cytosine Bases are diverse in organisms Ex: humans have 30.3 A Ecoli has 26 A Makes DNA a more credible candidate A=T G=C A=30.3 T=30.3 G=19.5 C=19.9 These became known as Chargaff’s rules 1. The base composition varies between species 2. Structure of a DNA Strand 1. Each DNA nucleotide monomer consists of a nitrogenous base (TACG) 2. Also consists of the sugar deoxyribose, and phosphate group 3. The phosphate group of one nucleotide is attached to the sugar of the next forming a BACKBONE of alternating phosphates and sugars from which the bases project
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4. 5’->3’, directionality, the 5 end is the phosphate group, and the 3 end is the OH sugar group Key Features of DNA Structure 1. “right handed” helix curves up to the right
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Biology exam 3 study guide kayla thomas - Biology Chapter...

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