• Chemical Cell Synchronization:
• Lovastatin: An inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase that depletes mevalonate. In cultured somatic cells, mevalonate starvation reversibly blocks cells in the $G_1$ phase of the cell cycle.
• (Nocodazole and Colchicine disrupt microtubules, arresting cells in M-phase).
• nalysis:
• (Lovastatin): Correct chemical for G1 synchronization.

Correct option: (3) Lovastatin.

• Interphase FISH Resolution:
• Fluorescent in situ hybridization (FISH) on metaphase chromosomes is limited to a mapping resolution of $\approx 1\text{--}3\text{ Mb}$ because chromatin is condensed up to 10,000-fold.
• During interphase, chromosomes are in their least condensed state (extended chromatin fibers), which substantially increases physical separation between closely adjacent DNA loci.
• This allows fine-scale mapping and ordering of genomic markers separated by only $50\text{--}100\text{ kb}$.

Correct option: (1) are the least condensed type of chromosome.

• Major Cyclin-CDK Complexes of Vertebrates:
• Throughout the eukaryotic cell cycle, distinct cyclin-CDK heterodimers control transitions through specific phase checkpoints:
• Cyclin D (G1 cyclin): Pairs with (IV) CDK4, CDK6 to promote passage through the restriction point in $\text{G}_1$ phase by phosphorylating Rb protein.
• Cyclin E (G1/S cyclin): Pairs with (I) CDK2 to trigger entry into S phase and initiate centrosome duplication.
• Cyclin A (S cyclin): Pairs with (III) CDK2 (and CDK1) to regulate DNA replication progression during S phase.
• Cyclin B (M cyclin): Pairs with (II) CDK1 (Cdc2) to form Maturation Promoting Factor (MPF), triggering mitosis entry.
• Conclusion: Matching: (A)-(IV), (B)-(I), (C)-(III), (D)-(II).

Correct option: (1) (A) - (IV), (B) - (I), (C) - (III), (D) - (II)