Condensation of chromosomes occurs during G1 phase
S phases
G2 phase
interphase
prophase

prophase

Explanation:

hope this helps

thinking it would be physical characteristics

enzyme active site and substrate specificity

enzymes bind with chemical reactants called substrates. there may be one or more substrates for each type of enzyme, depending on the particular chemical reaction. in some reactions, a single-reactant substrate is broken down into multiple products