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Beadle and Tatum

One gene one enzyme (polypeptide)

-Connected genes to proteins & shows how genes can influence observable traits

MacLeod & McCarty

Continued Griffiths work shown transforming principle was DNA

-Provided strong evidence that DNA carries genetic information

Chargaff

Amt A=T, AMT G=C

-Provided clue how DNA bases pair within molecule

*Franklin & Wilkins

Used X-ray diffraction to study DNA. Photo 51 provided evidence that DNA was helical and revealed measurements

*Watson and Crick

Used Franklin’s X-ray evidence, Chargaff’s rules and others to propose double-helix model of DNA w/ complementary base pairings

Griffith

Bacterial transformation; dead harmful bacteria can genetically change harmless bacteria into harmful

-Transforming principle could transfer hereditary information between cells

Levene

Identified components of nucleotide: sugar, phosphate group, nitrogenous based & DNA bases (ATCG)

-Helped scientists understand DNA’s chemical building blocks although proposed structure was incorrect.

Morgan

Used fruit flies to determine sex-linked inheritance (genes located on X chromosome

-Actual chromosomes inside cells

Miescher

Isolated substance from cell substance (nucleic → DNA)

Mendel

Traits inherited as separate factors (now called genes)

Described dom and recessive allies

Crick, Brenner, & colleagues

Frameshift mutation to show genetic information is read in groups of 3 bases (codons)

-How the order of DNA bases can provide instructions for building protein

Nirenberg & colleagues

Deciphered genetic code identifying which codons correspond to particular amino acids

-Explained how nucleotide sequence in genetic material determines amino acid sequence of a protein

Sanger

Developed DNA sequencing (method for determining exact order of nucleotides in DNA)

-Allowed researchers to directly read genes & study genetic information at sequence level

*Hershey and Chase

Used bacteriophages labeled w/ radioactive elements to show that DNA (instead of protein) enters bacteria and directs production of new viruses

-Confirmed DNA is genetic material

Meselson and Stahl

DNA replication is semiconservative; every new DNA molecules contains one og strand & one newly made

-Confirmed replication mechanism predicted by double-helix model