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GOALS:
After completing this module you should be able to:
- Recognize a nucleotide, the monomer of DNA, and its parts
- Describe how nucleotides are polymerized by the formation of phosphodiester bonds
- Recognize hydrogen bond donors and acceptors
- Determine the nucleotide sequence complementary to a given DNA sequence
The Form of Genetic Information in the Cell
Ever since the rediscovery of the genetics work of Gregor Mendel in the early 20th century, biologists had sought the chemical identity of the genetic material, the molecule that passes traits such as height, eye color, and blood type, from parents to offspring. Early on, it was assumed that proteins must be the carriers of genetic information. With 20 different side chains (See the Proteins 1 module), they were thought to be information-rich molecules that could pass on traits from generation to generation.
Experiments conducted in the 1940's and 1950's clearly showed that the genetic material was deoxyribonucleic acid (DNA)
, however. DNA is a polymer of nucleotides
: a backbone of alternating sugars and phosphate groups decorated with one of four aromatic nitrogen-containing bases
. The question remained, though: how could DNA, with only four bases, carry the enormous amount of information needed to describe complicated organisms?
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