Fact 1: Chromosomes are coiled structures made of DNA and proteins.

Fact 2: During prophase the chromosomes coil up.

Given the two facts above, answer the question "Structures coil when, and are made of DNA and proteins?" with the following options: 
- during the night
 - they bend
 - during prophase
 - during reproduction
 - an organism's body
 - solid, liquid, gas
 - during protein absorbtion
 - Veins and arteries.


 

   during prophase      