Concept 17 A gene is made of DNA.
In the 1920s, experiments showed that a harmless strain of bacteria can become infectious when mixed with a virulent strain of bacteria that had been killed. The dead bacteria apparently provide some chemical that "transforms" the harmless bacteria to infectious ones. This so-called "transforming principle" appeared to be a gene.
A team of scientists led by Oswald Avery at the Rockefeller Institute, rigorously followed up on these experiments in the 1940's. They found that a pure extract of the "transforming principle" was unaffected by treatment with protein-digesting enzymes but was destroyed by a DNA-digesting enzyme. This showed that the transforming principle is DNA — and, by extension, a gene is made of DNA. Still, many scientists were slow to accept this clear proof that DNA, not protein, is the genetic molecule.
DNA and proteins are key molecules of the cell nucleus.
One gene makes one protein.
A gene is made of DNA.
Bacteria and viruses have DNA too.
The DNA molecule is shaped like a twisted ladder.
A half DNA ladder is a template for copying the whole.
RNA is an intermediary between DNA and protein.
DNA words are three letters long.
A gene is a discrete sequence of DNA nucleotides.
The RNA message is sometimes edited.
Some viruses store genetic information in RNA.
RNA was the first genetic molecule.
Mutations are changes in genetic information.
Some types of mutations are automatically repaired.