Cell Cycle Regulation and Checkpoints

• Cyclins primarily promote the progression of the cell cycle through binding with cyclin-dependent kinases (Cdks).
• The G2 checkpoint ensures chromosomes have been properly replicated and are not damaged.
• A cell halts progression at the G1 checkpoint due to DNA damage and a lack of growth factors.
• Failure in the spindle checkpoint results in the cell progressing with unequal chromosome distribution.
• Tumor suppressor proteins like p53 halt the cell cycle when detecting DNA damage and can trigger apoptosis.
• The Rb protein regulates the cell cycle by binding to transcription factors, consequently blocking production of proteins for the G1/S transition.
• A cell failing the G2 checkpoint halts the cycle to repair DNA or complete replication.
• Overproduction of human growth hormone (HGH) leads to gigantism because of stimulated excessive cell division.
• Function of p21 in cell cycle regulation involves enforcing a halt by inhibiting the Cdk/cyclin complexes.
• The M checkpoint ensures chromosomes are properly attached to spindle fibers before anaphase.
• If p53 is nonfunctional, cells are more likely to undergo uncontrolled division.
• Cell division can be initiated by cell size reaching a critical threshold.
• The G1 phase is the longest in rapidly dividing human cells.
• Cdks primarily function to regulate the cell cycle through phosphorylation of other proteins.
• Specialized cells like neurons typically enter the G0 phase instead of continuing the cell cycle.
• Cyclins are degraded by cytoplasmic enzymes after helping regulate a checkpoint.
• When a cell's surface-to-volume ratio becomes too small, the cell divides to become more efficient.
• A failure at the G1 checkpoint may allow cells with damaged DNA to continue to divide.
• Negative regulatory proteins key role stops the cell cycle until damaged DNA is repaired.
• The main purpose of the S phase in the cell cycle is DNA replication.

Explore cell cycle regulation, checkpoints (G1, G2, M), and the roles of cyclins, Cdks, and tumor suppressors like p53 and Rb. Understand how these mechanisms ensure proper cell division and prevent errors such as unequal chromosome distribution. Learn about the impact of growth factors and the consequences of checkpoint failures.