DNA as Genetic Material - Key Experiments (Griffith, Avery-MacLeod-McCarty, Hershey-Chase)

Vocabulary flashcards covering the discovery of DNA as the genetic material and the major experiments (Griffith, Avery–MacLeod–McCarty, Hershey–Chase) that established DNA as the hereditary material, plus related concepts.

DNA

The molecule that stores genetic information and, in these experiments, is shown to be the transforming substance and genetic material.

S (Smooth) Strain

Encapsulated, virulent Streptococcus pneumoniae that kills mice.

R (Rough) Strain

Non-encapsulated, nonpathogenic Streptococcus pneumoniae.

Heat-killed S Strain

Heat-killed pathogenic bacteria used in Griffith's experiments to test transformation.

Transforming Factor

Hypothetical substance transferred from dead virulent bacteria to live nonvirulent bacteria that causes transformation.

Griffith's Experiment

Demonstrated transformation by showing heat-killed S could convert R into S.

Avery–MacLeod–McCarty (1944)

Extended Griffith; showed DNA is the transforming principle by degrading other macromolecules and observing loss of transformation.

Deoxyribonucleodepolymerase (DNase)

DNA-degrading enzyme; its ability to destroy transforming power indicated DNA is the transforming factor.

Hershey–Chase (1952)

Demonstrated DNA, not protein, is the genetic material using radiolabeled phages and E. coli.

T2 Bacteriophage

A virus that infects E. coli and was used in Hershey–Chase experiments.

32P

Radioactive phosphorus used to label DNA in Hershey–Chase experiments.

35S

Radioactive sulfur used to label protein coat in Hershey–Chase experiments.

Phage DNA Entry

In Hershey–Chase, only labeled DNA enters the bacterial cell and directs replication.

Capsid/Protein Coat

Protein shell of a virus that encases its genetic material.

Transformation (biology)

Process by which cells take up external DNA and incorporate it into their genome.

Nucleotides

The four monomers of DNA (adenine, thymine, cytosine, guanine).

Morgan’s Theory of the Gene

Questioning whether a gene is a small chemical molecule or a larger organic matter; early debate on the gene’s nature.

Chromosome Composition

Chromosomes contain DNA and protein; historical view that protein may be more abundant than DNA, despite DNA having four nucleotides.