Biology · Cell Cycle and Cell Division · NEET
Spindle fibres attach to the KINETOCHORE, not directly to the centromere. NCERT says small disc-shaped structures on the surface of the centromere are the kinetochores, and these serve as the sites of attachment of spindle fibres. The centromere is the constriction that holds the two sister chromatids together and carries the kinetochore, but the fibres physically dock on the kinetochore. NEET repeatedly sets 'attach to centromere' as the wrong distractor.
The metaphase plate is not a real structure. It is the imaginary flat plane at the middle (equator) of the cell along which all chromosomes get aligned during metaphase. NCERT defines it as 'the plane of alignment of the chromosomes at metaphase'. Do not confuse it with the cell plate, which forms much later during cytokinesis in plant cells.
Double. At metaphase each chromosome is still made of TWO sister chromatids held together by the centromere. One chromatid's kinetochore is connected to spindle fibres from one pole and the sister chromatid's kinetochore to fibres from the opposite pole. The centromere splits only later, at anaphase, giving single-chromatid daughter chromosomes.
By metaphase the condensation of chromosomes is complete, so they are the thickest and most clearly visible under the microscope. NCERT states this is the stage at which the morphology of chromosomes is most easily studied — that is why karyotypes are prepared from metaphase chromosomes.
They point to the same location but mean slightly different things. The equator is the middle region of the spindle; the metaphase plate is the specific imaginary plane at that equator where the chromosomes actually line up. In NEET options 'arrangement at equator' and 'metaphase plate' both refer to metaphase alignment.
Spindle fibres attach to kinetochores of chromosomes during
Doubling of the number of chromosomes can be achieved by disrupting mitotic cell division soon after
Select the incorrect statement with reference to mitosis:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
The nuclear envelope is fully gone, chromosome condensation is complete, spindle fibres attach to the kinetochores, and all chromosomes line up at the metaphase plate (the equator of the cell).
It is not made of anything physical. It is an imaginary flat plane at the middle of the cell where the chromosomes align. Do not confuse it with the cell plate of cytokinesis.
Two sister chromatids, held together by the centromere. They separate only in anaphase when the centromere splits.
To the kinetochores — small disc-shaped structures on the surface of the centromere — one chromatid to fibres from one pole and its sister to fibres from the opposite pole.
It is the stage where chromosome morphology is clearest, where the metaphase plate and kinetochore attachment are defined, and NEET asks these facts almost every year, often with the centromere-vs-kinetochore trap.
