Which statement best describes how Watson and Crick's model used other scientists' work to create a model of DNA? They used Chargaff's rule to determine that it contains ribose sugar.
They used Franklin's photo to determine that DNA was a double helix.
They used Levene's work to determine the number of base pairs in each strand.
They used Nirenberg and Matthei's studies to determine that DNA is made of nucleotides.

Why are small quantities of chlorofluorocarbons so harmful to the ozone layer? a. the chlorofluorocarbons act like ultraviolet radiation causing large amount of ozone to be produced. b. the chlorine from the chlorofluorocarbons reacts with free molecules of oxygen causing a stop in ozone production c. free oxygen atoms can replace the chlorine in chlorine monoxide, releasing a free atom of chlorine which can then recombine with an oxygen atom in ozone, destroying more ozone. d. chlorofluorocarbons absorb ultraviolet radiation, preventing the formation of ozone select the best answer from the choices provided

What have we learned from fossil evidence about evolution? a) it is an abrupt change. b)the process is observable. c) it takes place during one lifetime only. d)the most complex traits are always selected.

What is the similarities and differences between bacteria and eukaryote?