Question

Which of the following occurs during late prophase/early prometaphase?

a) continuous kinetochore microtubule shortening
b) formation of a contractile ring
c) centrosome duplication
d) the kinetochore attachment checkpoint is preventing transition to metaphase
e) M-Cdk phosphorylation of lamins in the nuclear envelope

Answer 1

During late prophase/early prometaphase, continuous kinetochore microtubule shortening, kinetochore attachment checkpoint, and M-Cdk phosphorylation of lamins in the nuclear envelope occur.

Step-by-step explanation:

During late prophase/early prometaphase, the following occurs:

1. Continuous kinetochore microtubule shortening: Microtubules from the mitotic spindle attach to the centromeres of sister chromatids, forming kinetochores. These kinetochores then shorten, pulling the chromosomes towards opposite poles of the cell.
2. The kinetochore attachment checkpoint is preventing transition to metaphase: At this stage, the kinetochores are still in the process of attaching to microtubules. The attachment checkpoint ensures that all chromosomes are properly attached before moving to the next stage, metaphase.
3. M-Cdk phosphorylation of lamins in the nuclear envelope: The nuclear envelope disintegrates during late prophase/early prometaphase. This is facilitated by the phosphorylation of lamins, which are proteins that provide structural support to the nuclear envelope.