Genes, which are the molecular units of heredity, are composed of specific sequences of four

Nucleotide bases.

Explanation:

Unique sequences of bases makes up a nucleotide. These nucleotide sequencing are used by DNA as a genetic code of information that determines type of cells, proteins and the whole organismal structure.

There are four nucleotide bases, Adenine and guanine termed purines are big, cytosine and thymine called pyrimidines are small. A purine pairs with a pyrimidine, such that adenine pairs with thymine and guanine pairs with cytosine. The bases are the same but each DNA uniqueness lies in the sequence of base pairing.

what statement best describes the difference between the sympathetic and parasympathetic nervous systems?

the sympathetic nervous system prepares the body for intense physical activity and is often referred to as the fight-or-flight response. the parasympathetic nervous system has almost the exact opposite effect and relaxes the body and inhibits or slows many high energy functions.