Final answer:
When a G1 cell sustains genetic damage, checkpoint mechanisms may repair or halt the cell cycle. The cleavage furrow, guiding cell division in cytokinesis, is formed by actin microfilaments in animal cells and is unrelated to G1 phase damage.
Step-by-step explanation:
When a normal G1 cell sustains genetic damage, it is likely that specific checkpoint mechanisms within the cell cycle will be activated to either repair the damage or prevent the cell from entering S phase and replicating damaged DNA. If the damage cannot be repaired, the cell may undergo apoptosis to prevent the propagation of genetic errors. The formation of the cleavage furrow is not directly related to genetic damage in G1 phase but is rather a part of cytokinesis, the process that occurs after mitosis where the cell divides. The creation of the cleavage furrow is guided by the arrangement of actin microfilaments contracting in a ring inside the plasma membrane at the former metaphase plate, ensuring that it forms in the same plane as the two spindle poles of the dividing cell. The correct option in the context of cleavage furrow formation during normal cytokinesis is C: Astral microtubules contact the membrane and activate proteins to form a central furrow.