One of four bases. The 4 bases are not present in equal amounts. Amounts are different for each species. Beans have 30 times more DNA than you do. There is a proofreading function to correct mistakes.
Replication is semiconservative .
1 old and 1 new strand in each. G cytosine C RNA is usually single stranded. DNA is usually double stranded, RNA is usually single stranded. RNA uses uracil instead of thymine. In DNA the sugar is deoxyribose, in RNA the sugar is ribose.