The Chemical Nature of DNA and Its Historical Context

DNA

The genetic material capable of storing large amounts of complex information, accurate replication, and variation between individuals and species.

Mendel

Scientist who proposed a theory for the inheritance of characters in 1865.

Friedrich Miescher

Scientist who isolated DNA from the nuclei of white blood cells in pus in 1869.

Albrecht Kossel

Scientist who determined that DNA contains the nitrogenous bases A, G, C, and T in the late 1800s.

Levine

Scientist who determined the structure of nucleotides and proposed the tetranucleotide hypothesis in 1910.

Thomas Hunt Morgan

Scientist who showed that genes are on chromosomes in 1915.

Griffith

Scientist who demonstrated the transforming principle in 1928.

Avery, MacLeod, and McCarty

Scientists who demonstrated that the transforming principle is DNA in 1944.

Chargaff

Scientist who discovered that in DNA, the nucleotide composition varies between species and %A = %T and %C = %G in 1948.

Hershey and Chase

Scientists who demonstrated that DNA is the genetic material in bacteriophages in 1952.

Watson and Crick, Franklin and Wilson

Scientists who determined the structure of DNA in 1953.

Frankel-Conrat and Singer

Scientists who showed that some viruses use RNA as the genetic material in 1956.

Streptococcus pneumoniae

Bacterium used in Griffith's experiments, where virulent strains have a polysaccharide coat and non-virulent strains lack the coat.

Bacterial Transformation

The process where genetic material is transferred from one bacterium to another, as observed in Griffith's experiments.

RNase

Enzyme that degrades RNA, used in experiments to show that RNA is not needed to convert IIR to IIIS bacteria.

Proteases

Enzymes that degrade proteins, used in experiments to show that protein is not needed to convert IIR to IIIS bacteria.

DNase

Enzyme that degrades DNA, used in experiments to show that DNA is needed to convert IIR to IIIS bacteria.

IIR

Intermediate Infection Reaction

IIIS

Superinfection Reaction

Transforming Principle

DNA as the genetic material responsible for transformation

Bacteriophages

Viruses infecting bacteria, consisting of DNA and protein

Phosphorus

Present in DNA but absent in bacterial proteins

Sulfur

Present in bacterial proteins but absent in DNA

Radioactive Phage

Phage labeled with P32 or S35 for tracking DNA or protein

Watson and Crick

Scientists credited with the double helix DNA model

Nobel Prize 1962

Awarded for the DNA structure discovery

Rosalind Franklin

Contributor to DNA structure through X-ray diffraction

Maurice Wilkins

Shared Nobel Prize for DNA structure elucidation

X-ray Diffraction

Method revealing DNA helical shape and base projection

Nucleotide

Repeating unit of DNA or RNA with sugar, base, and phosphate

Phosphodiester Bonds

Strong covalent bonds linking nucleotides in DNA or RNA

Polarity

DNA's 5' to 3' directionality for synthesis and replication

Hydrogen Bonds

Hold DNA strands together; 2 for A-T and 3 for G-C pairs

Complementarity

Non-identical base pairing essential for replication and transcription

Semi-Conservative Replication

Parental DNA strands serve as templates for new double helices

Secondary Structures

Stem-loop formations in DNA and RNA for functional complexity

Major Grooves

Regions in DNA helix crucial for protein binding and recognition

Polynucleotide Strands

Long chains of nucleotides storing vast genetic information

Purines

Adenine and Guanine; double carbon-nitrogen ring bases

Pyrimidines

Cytosine, Thymine, and Uracil; single carbon-nitrogen ring bases

Ribose

Sugar in RNA with OH group at 2'C

Deoxyribose

Sugar in DNA lacking OH group at 2'C