Practice question

Colchicine is not considered fusogen, unlike true fusogenic agents that promote membrane merging of protoplasts. Legitimate fusogens include polyethylene glycol PEG high molecular weight polymer that dehydrates membrane interface creating calcium bridges neutralizing negative charge inducing lipid mixing upon dilution, high concentration calcium ions at alkaline pH around 10.5 similar mechanism reducing electrostatic repulsion, and inactivated Sendai virus bearing fusogenic HN and F glycoproteins that merge animal and plant membranes albeit rarely used now due to biohazard handling. Electrical pulses via electrofusion also physically fuse membranes through reversible dielectric breakdown not chemical fusogen definition but effective. Colchicine mechanism distinct: it binds tubulin dimer with high affinity blocking microtubule assembly disrupting spindle formation during mitosis leading to polyploidy chromosome doubling, classified as antimitotic alkaloid rather than membrane fusogen. It does not destabilize lipid bilayer nor create intermembrane coalescence step necessary for protoplast fusion. Hence in lists evaluating fusogenic compounds colchicine stands out as non fusogenic used for ploidy manipulation rather than heterokaryon formation, correctly identified as answer for which is NOT fusogen.