Individual chromosomes are clearly visible in which phase?
Visibility of individual chromosomes under light microscope depends on degree of condensation regulated by condensin complexes and histone modifications across cell cycle. Interphase chromatin exists as 10 nanometer beads-on-string fiber further folded into 30 nanometer fiber and looped domains anchored to nuclear matrix, occupying distinct chromosome territories where active transcription and replication occur, but overlapping extensively making individual chromosomes unresolvable. Entry into M phase, triggered by cyclin B-CDK1 rising activity, activates condensin I and II ATPases that extrud
Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 17: Mitotic Chromosome Condensation.
