With the advent of technology, researchers have been able to focus their attention on the messengers of the brain, neurotransmitters. researchers can introduce to alter the activity level of a neurotransmitter in order to analyze the effects that are opposite of those usually produced by that neurotransmitter.

Antagonists

Explanation:

Antagonist induce the opposite effect to that of the neurotransmitter. They exert their effects by binding and altering the site at which the neurotransmitter functions. The antagonist may act competitive or non-competitive meaning they bind to the active site or non-active site, respectively.  

the answers are as following:

1. c. double helix, nucleosome, coil, supercoil, chromosome

2. b. g2 phase, preparation for mitosis

3. d. interphase consists of the g1, s, and g2 phases

4. c. metaphase

5. a. chromosomes are duplicated before cell division so that each new daughter cell has a complete set

answer; (b) clear with a slight blue tint;