In 1952, Rosalind Franklin took an X-ray photograph that revealed the structure of DNA. James Watson and Francis Crick followed up on this discovery in 1953. They discovered that the molecule has a specific shape that can best be described as — A. a single strand containing 4 different bases that vary depending on the type of DNA

B. ladder-shaped, containing 5 nitrogenous bases that bond to one another

C. triple-stranded, with bonds between each strand holding the three strands together

D. double-stranded and twisted, with bases bonded to other bases which hold the strands together

(me out over the last several centuries, scientists have made the following broad observations while investigating several branches of the life sciences: -the fossil record shows that different types of organisms have existed at different times in earth's history. -many organisms have similar body structures that seem to be adapted to different ways of living in their environment. -organisms of different species often share similarities in stages of embryonic development. -many species share genetic similarities, and almost all organisms use the same basic building blocks to construct proteins. -often, the extent of two species' similarities can be predicted from their geographic closeness to each other. -a great deal of change has been observed among species that have experienced strong selective pressures through many generations. scientists have carefully considered and rigorously tested the observations listed above. when scientists offer a of these observations, they are making 1.) testable explanation, deductive explanation 2.) scientific interference, scientific law