Chapter 13 Active Reading Guide:

The Molecular Basis of Inheritance Section 1

a) What are the two chemical components of chromosomes?

b) Why did researchers originally think that protein was the genetic material?

c) Distinguish between the virulent and nonvirulent strains of Streptococcus pneumoniae studied by Frederick Griffith.

(A) : DNA and protein

(B) : The case for proteins appeared stronger until the 1940s, especially since biochemists had identified them as a class of macromolecules with great heterogeneity and function specificity, essential requirements for the hereditary material. Moreover, little was known about nucleic acids, the physical and chemical properties of which seemed far too uniform to account for the multitude of specific hereditary traits of each organism

(C) : Virulent strains are pathogenic (causing disease), whereas non-virulent strains are non-pathogenic (harmless) strains.