Anaphase: Chromatid Separation — NEET Biology
✅ Asked in NEET 2025What is the main function of the spindle fibres during mitosis?
What is the main function of the spindle fibres during mitosis?
Answer & NCERT explanation
Correct answer: A — To separate the chromosomes
The primary function of spindle fibres during mitosis is chromosome separation. Spindle fibres attach to kinetochores and pull sister chromatids to opposite poles during anaphase, ensuring equal distribution of genetic material. DNA synthesis occurs during S phase, not during mitosis itself. DNA repair is not the main mitotic function, and cell growth regulation involves different cellular mechanisms. The spindle apparatus is specifically evolved for the mechanical task of chromosome segregation during cell division.
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At the onset of anaphase, each chromosome arranged at the metaphase plate is split simultaneously and the two daughter chromatids, now referred to as daughter chromosomes of the future daughter nuclei, begin their migration towards the two opposite poles. As each chromosome moves away from the equatorial plate, the centromere of each chromosome remains directed towards the pole and hence at the leading edge, with the arms of the chromosome trailing behind. Thus, anaphase stage is characterised by
During anaphase, sister chromatids separate at the centromere and move toward opposite poles as independent chromosomes. The centromere leads the movement, making the chromosome V-shaped or J-shaped depending on centromere position. Students often confuse anaphase I (homologous chromosomes separate) with anaphase II (sister chromatids separate), or mistakenly think the chromosome arms lead the movement. Remember: centromere always leads, and in mitotic anaphase, sister chromatids (not homologs) separate. This concept is fundamental to understanding chromosome movement mechanics and distinguishing between meiotic stages.
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