Attachment of spindle fibers to kinetochores of
chromosomes becomes evident in:
AI-generated explanation. Check against your textbook.
Explanation:
In mitosis, the kinetochores on chromosomes attach to spindle microtubules as the chromosomes align. This attachment becomes evident when the chromosomes align at the middle of the cell, i.e., in metaphase, with kinetochores held on by spindle fibers from opposite poles. Thus, the visible connection between kinetochores and spindle fibers is most evident during metaphase of cell division, as per NCERT description.
🧠 Did You Know?
Metaphase is characterized by chromosomes lining up at the equator, with kinetochores attached to microtubules from both poles.
💡 NCERT Memory Line:
“Chromosomes move to the equator and become arranged at metaphase plate; spindle fibers attach to kinetochores.”
AI-generated explanation. Check against your textbook.
Explanation:
Option 2 is incorrect because in C4 plants, RuBisCO is active mainly in bundle sheath cells, not in mesophyll cells. In C4 photosynthesis, CO2 is initially fixed in mesophyll cells into a 4‑carbon compound, which is then released to bundle sheath cells where RuBisCO fixes CO2 in the Calvin cycle.
🧠 Did You Know?
RuBisCO is a bifunctional enzyme—it can act as both a carboxylase and an oxygenase, catalyzing CO2 fixation as well as O2 reaction with RuBP.
💡 NCERT Memory Line:
RuBisCO fixes CO2 in the Calvin cycle; ATP and NADPH are used in regenerating RuBP, not in the direct carboxylation step by RuBisCO.