G vs guanine

G and guanine both are nouns.

Word	Noun	Adjective	Verb	Adverb
G	Yes	No	No	No
guanine	Yes	No	No	No

As nouns, G and guanine are synonyms defined as:

G (noun)	guanine (noun)
the 7th letter of the Roman alphabet	a purine base found in DNA and RNA; pairs with cytosine
the cardinal number that is the product of 10 and 100
a unit of information equal to 1024 mebibytes or 2^30 (1,073,741,824) bytes
a unit of information equal to 1000 megabytes or 10^9 (1,000,000,000) bytes
(physics) the universal constant relating force to mass and distance in Newton's law of gravitation
one of the four nucleotides used in building DNA, also known as deoxyguanylate, or dGMP; all four nucleotides have a common phosphate group and a sugar (ribose)
a purine base found in DNA and RNA; pairs with cytosine