How Traits Are Inherited.

In the early 1940s researchers made a major breakthrough in genetics, the branch of biology that deals with inherited characteristics in all forms of life. They established how hereditary information is carried by chromosomes, threadlike structures composed of nucleic acids and proteins that exist within the nucleus of the cell. Each chromosome is made up of individual genes that determine specific hereditary factors (color of hair and eyes, for example). The major question for geneticists in the 1940s was what gives these strands of proteins and nucleic acids the special ability to transmit information about an organism's traits. This question would not be answered entirely until the early 1950s, but important strides were made in the 1940s, as geneticists made discoveries that lay behind James Watson and Francis Crick's groundbreaking discovery in 1952 of the double-helix structure of DNA (deoxyribonucleic acid...