Biology - Genes
The general structure of a nucleotide
A gene  is a functional section of the DNA  of a chromosome  that
codes for the production of a particular protein. DNA is composed of units
called nucleotides,  which themselves are composed of sub-units: a sugar
molecule (deoxyribose), a phosphate group, and one of four nitrogen bases.
The nucleotides in a single strand of DNA are linked together by means of
chemical bonds between the phosphate group of one nucleotide and the ribose
sugar of the next. In this way, a polynucleotide chain or backbone of ...
_-ribose-phosphate-ribose-phosphate-ribose-phosphate -_ ... is formed with
the bases attached to each ribose sugar. A complementary strand of DNA
bonds to the first strand according to the base-pairing rule: A of one
strand with T of the other (held by 2 hydrogen bonds), and C and G (held by
3 hydrogen bonds), making a twisted or spiral double helix.
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