Final answer:
The stage in mitosis where the nuclear envelope disintegrates and sister chromatids attach to spindle microtubules is called prometaphase.
Step-by-step explanation:
Stage of Mitosis with Nuclear Envelope Disintegration and Chromatid Attachment
The stage in mitosis where the nuclear envelope disintegrates and the sister chromatids become attached to microtubules from opposite centrosomes is known as prometaphase. During prometaphase, the nuclear envelopes are completely broken down and disappear, allowing the spindle to fully form. Each sister chromatid forms an individual kinetochore that attaches to microtubules emanating from opposite poles. The mitotic spindle, which originates from the centrosomes, plays a crucial role by not only capturing the chromosomes but also by facilitating their separation and the elongation of the cell.