1. DNA_Study_Guide_xx.pptx - Unit 2 DNA Part 1 DNA Structure DNA Chemistry and Chromatin Concepts for Study How did investigators pinpoint DNA as the

1. DNA_Study_Guide_xx.pptx - Unit 2 DNA Part 1 DNA...

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Unit 2. DNA
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Part 1: DNA Structure, DNA Chemistry and Chromatin
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Concepts for Study How did investigators pinpoint DNA as the genetic material? Who were the contributors to the elegant Watson-Crick-Franklin model of DNA structure, and what were their contributions? How does DNA structure provide for the storage of genetic information? How is DNA compacted?
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DNA is a common denominator for life on earth
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Modern DNA studies Focus on Genomes, Proteomes and Gene Function New insights into the relatedness of species and the origin of life
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Three Domains of Life DNA tells us who is related to whom
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The discovery of DNA as the genetic material and the structure of DNA Bring us keen insights into the scientific process Create an understanding of the chemical structure and the nature of the inheritance molecule Raise questions about ethics and scientific conduct
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Recall… Chromosomes are complexes of DNA and Protein. Once the composition was determined in the 1800’s, scientists began wondering, which part of the chromosome is the genetic material?
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Are genes composed of DNA or protein? Protein was in the lead: 20 different subunits (amino acids) make up proteins – greater potential variety of combinations. Only four different subunits (nucleotides) make up DNA Chromosomes contain more protein than DNA by weight
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Experiments on the path to discovery: DNA as the substance of genes 1928 – Frederick Griffith: experiments with smooth (S), virulent strain Streptococcus pneumoniae , and rough (R), nonvirulent strain demonstrated transfer of genetic material, but what was the genetic material? 1944 – Oswald Avery, Colin MacLeod, and MacIyn McCarty: Determined that DNA is the transformation material with Griffith’s system 1952 – Alfred Hershey and Martha Chase: Confirmed that DNA was inherited with phage experiments
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Griffith experiment Streptococcus pneumoniae
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Griffith concludes: A “Transformng Priciple” is present in the S cells that is transferred to the R cells What was this “Principle” that could convey characteristics to the R strain?
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Avery, MacLeod, McCarty Experiment This result by Griffith was analyzed further and the components looked at piece by piece to find the one that could transform…
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Avery et al. The scientists examined the transforming reaction of Griffith They digested (in turn) lipids, proteins and carbohydrates then repeated the experiment, but transformation still occurred the transforming principle must be a nucleic acid
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So DNA was the transforming principle! =genetic material But don’t I remember something about an exception with RNA?
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RNA may be the genetic material for some viruses (never for cells)
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