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Chapter 10 - Nature of the Gene and Genome (Spring 2011)

Were studying chromosomes discovered that stains that

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Unformatted text preview: chromosomes discovered that stains that coloured chromosomes also worked on nucleic acids Chromosomes consisted of protein and nucleic acids Proteins were complex and had specific and varied catalytic activity DNA was a repeat of four nucleotide building blocks Many scientists though DNA was too simple to be the genetic material favoured protein 1920s: studying pathogenic bacteria found transforming agent was DNA dead lethal bacterial could transform living non lethal bacteria to lethal form (the non lethal bacteria picked up DNA from the lethal one and transformed) Hershey and Chase confirmed DNA as the genetic material through studies of bacteriophage 2 o o o o o o o o o o o o o o o o Viruses inject their genetic material into hosts bacteriophage was just proteins and DNA so genetic material had to be one or the other Genetic material must pass from phage into bacterial cell and also passed on to next generation of phages Hershey and Chase made 2 batches of bacteriophages one with radioactively labelled DNA and one with radioactively labelled protein They allowed the phages to infect bacteria then separated the phage coats from the cells Radioactive DNA: radioactivity mainly in cells, most passed to future phage generations Radioactive proteins: radioactivity mainly in remaining coats, very little in offspring DNA is the genetic material in all organisms Structure: the nucleotide is the building block of DNA Nucleotide: consists of a phosphate, sugar and either a pyrimidine or a purine nitrogeneous base There are 2 different pyrimidines : thymine (T) and cytosine (C) There are 2 different purines: adenine (A) and guanine (G) Nucleotides have a polarized structure where the ends are called the 5 and the 3 Nucleotides are linked into nucleic acid polymers sugar and phosphates are linked by 3 ,5 -phosphodiester bonds they project out like stacked shelves Originally, we thought bases simply repeated too simple to be genetic information Chargaff showed that the ratio of bases varied between species but was constant within a species he established rules after doing base composition analysis In base composition analysis he figured the number of adenine = number of thymine and number of cytosine = number of guanine DNA o o o o o o o o o o o o o Watson-Crick proposal: the DNA is a double helix DNA is composed of 2 chains of nucleotides they spiral around each other forming a pair of right hand helices The 2 chains are antiparallel they run in opposite directio...
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