When mitotic Cdk-cyclin is injected into cells that have just emerged from S pha

Question

When mitotic Cdk-cyclin is injected into cells that have just emerged from S phase, chromosome condensation and nuclear envelope breakdown occur immediately, rather than after the normal G2 delay of several hours.

Select the four correct statements.

Mitotic Cdk-cyclin is normally activated at the end of S. It is possible to trigger chromosome condensation and nuclear envelope breakdown prematurely by experimentally introducing mitotic Cdk-cyclin into cells that have just emerged from G2 phase. Phosphorylation of condensins and lamins prevents chromosome condensation and nuclear envelope breakdown. Mitotic Cdk-cyclin is normally activated at the end of G2. Mitotic Cdk-cyclin catalyzes the phosphorylation of condensins and lamins. It is possible to trigger chromosome condensation and nuclear envelope breakdown prematurely by experimentally introducing mitotic Cdk-cyclin into cells that have just emerged from S phase. Phosphorylation of condensins and lamins contributes to chromosome condensation and nuclear envelope breakdown. Mitotic Cdk-cyclin inhibits the phosphorylation of condensins and lamins.

Explanation / Answer

Ans-
1. Mitotic Cdk-cyclin catalyzes the phosphorylation of condensins and lamins.
2. Phosphorylation of condensins and lamins contributes to chromosome condensation and nuclear envelope breakdown.
3. It is possible to trigger chromosome condensation and nuclear envelope breakdown prematurely by experimentally introducing mitotic Cdk-cyclin into cells that have just emerged from S phase.
4. Mitotic Cdk-cyclin is normally activated at the end of G2.
Explanation:
Cyclin-dependent kinase 1 (Cdk1) is activated at the end of G2 that initiates mitotic entry. The mitotic Cdk cycle 1- phosphorylated lamin in the nuclear lamina that induces depolarization and condensin induces polymerization. Cyclin B- Cdk1 involve chromatin condensation, nuclear envelop breakdown, fragmentation of Golgi apparatus and spindle formation.

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