What is the key role of cyclins in the cell cycle?

What is the key role of cyclins in the cell cycle?

• A. They synthesize DNA
• B. They activate cyclin-dependent kinases
• C. They repair DNA damage
• D. They enhance cell growth

Answer: (B)

Cyclins play a crucial role in the regulation of the cell cycle by activating cyclin-dependent kinases (CDKs). These proteins are essential for the progression through various phases of the cell cycle, including G1, S, G2, and M phases. When cyclins bind to CDKs, they induce a conformational change that activates the kinase activity of CDKs, allowing them to phosphorylate target proteins that drive the cell cycle forward. The act of binding to CDKs is tightly regulated by the levels of cyclins, which fluctuate throughout the cell cycle. For instance, specific cyclins are produced at particular times, ensuring that CDKs are activated only in the appropriate phase of the cell cycle. This precise timing is crucial for normal cell division and helps maintain genomic integrity. Other choices describe important cellular processes but do not accurately reflect the primary role of cyclins in the cell cycle. Cyclins do not directly synthesize DNA, repair DNA damage, or enhance cell growth; rather, they serve primarily as regulatory subunits that control the activity of CDKs to facilitate the orderly progression through the cell cycle.

Cyclins play a crucial role in the regulation of the cell cycle by activating cyclin-dependent kinases (CDKs). These proteins are essential for the progression through various phases of the cell cycle, including G1, S, G2, and M phases. When cyclins bind to CDKs, they induce a conformational change that activates the kinase activity of CDKs, allowing them to phosphorylate target proteins that drive the cell cycle forward.

The act of binding to CDKs is tightly regulated by the levels of cyclins, which fluctuate throughout the cell cycle. For instance, specific cyclins are produced at particular times, ensuring that CDKs are activated only in the appropriate phase of the cell cycle. This precise timing is crucial for normal cell division and helps maintain genomic integrity.

Other choices describe important cellular processes but do not accurately reflect the primary role of cyclins in the cell cycle. Cyclins do not directly synthesize DNA, repair DNA damage, or enhance cell growth; rather, they serve primarily as regulatory subunits that control the activity of CDKs to facilitate the orderly progression through the cell cycle.