Molecular Biology l Introduction Definitions History Central Dogma

Molecular Biology l Introduction – Definitions – History – Central Dogma

Molecular Biology l Definitions – Chromosomes – DNA – Gene – Genotype – Phenotype

Molecular Biology l Chromosomes – The structure in cells that carries hereditary information – Composed of DNA and protein – Prokaryotic - circular – Eukaryotic - linear

Molecular Biology l DNA – Nitrogenous base (4 bases - A, T, G & C – Deoxyribose sugar – Phosphate – Nitrogenous bases are paired » AT » GC – Double helix structure

Molecular Biology l Genes – Segments of DNA – Functional or regulatory – Mutability and variation

Molecular Biology l Genotype – The genetic make-up of an organism; the information that codes for all the characteristics of an organism l Phenotype – The expression or physical manifestation of a gene; how it appears

Molecular Biology Molecular biology seeks to understand the molecular or chemical basis of genetics l History of molecular biology is a melding of biochemistry, especially nucleic acid biochemistry and genetics l

Molecular Biology l Biochemistry – – Meischer Avery & Mac. Leod Hershey & Chase Watson & Crick l Genetics – – – – Mendel Sutton Morgan Griffith Delbruck Beadle & Tatum & Lederberg

Molecular Biology - Genetics l Mendel (1865) – Fluid vs. particulate inheritance – Studied pure breeding pea plants – Law of Segregation – Law of Independent Assortment – Rediscovered by de Vries & others

Molecular Biology

Molecular Biology

Molecular Biology - Genetics Cross of pure breeding purple flowers with pure breeding white flowers produces all purple plants with genotype Pp; crossing Pp plants produces following distribution: P p P PP purple Pp purple pp white

Molecular Biology - Genetics l Walter Sutton (1902) – Studied meiosis in grasshoppers (insects have large readily observable chomosomes) – Observed that chromosomes behave in manner similar to segregation of hereditary material – Found that chromosomes occur in morphologically similar pairs – Pairs separate during meiosis

Molecular Biology - Genetics

Molecular Biology - Genetics l Morgan – Developed modern science of genetics – Used fruit flies because they had a shorter generation time than peas – Discovered sex-linkage – Students developed techniques of mapping genes on chromosomes

Molecular Biology - Genetics l Griffith – discovered transformation in 1927 – is a means of genetic transfer in microorganisms – a process by which a nonpathogenic strain is transformed into a pathogenic strain

Molecular Biology - Genetics

Molecular Biology - Genetics l Delbruck – developed quantitative methods for analysis of bacteriophage; viruses of bacteria – organized course to teach biologists methods at Cold Spring Harbor resulting in a large number of biologists trained in molecular techniques

Molecular Biology - Genetics l Beadle & Tatum – developed Neurospora as an experimental organism – established one gene one enzyme hypothesis – generation time is even shorter with Neurospora

Molecular Biology - Genetics

Molecular Biology - Genetics

Molecular Biology - Genetics

Molecular Biology - Genetics l Tatum & Lederburg – discovered conjugation in bacteria – Led to genetic map of E. coli – E. coli became widely used in molecular biology

Molecular Biology Biochemistry l Meischer (1869) – Austrian doctor – isolated a substance called “nuclein” from the nuclei of cells obtained from the pus of surgical bandages – found to contain nitrogenous chemicals, sugar and phosphate

Molecular Biology Biochemistry l Avery & Mac. Leod (1944) – isolated Griffith’s transforming factor to a high degree of purity – characterized transforming factor using highly purified enzymes – found transforming factor to be DNA

Molecular Biology

Molecular Biology Biochemistry l Hershey & Chase (1952) – used newly developed radioisotopes » 35 S » for protein 32 P for nucleic acid – labeled bacteriophage (a virus of bacteria) – found 32 P went into cells but 35 S did not implying that nucleic acid transfer information to cell for new bacteriophages

Molecular Biology Biochemistry l Watson & Crick (1953) – used X-ray crystallography to study structure of DNA – by combining chemical data and X-ray data were able to construct a model of DNA – structure inferred function leading to Central Dogma