The UK's most valuable monument is deemed to be the 1,000-year-old Tower of London, which is worth an estimated Â£56billion to the British economy and came it at number five in the list of European list. Its value is six times more than its nearest rival the Colosseum in Rome, which is valued at Â£72billion.
Cell cycle checkpoints are control mechanisms in eukaryotic cells which ensure proper division of the cell.
A second such checkpoint occurs at the G2 phase following the synthesis of DNA in S phase but before cell division in M phase. Cells use a complex set of enzymes called kinases to control various steps in the cell cycle. Cyclin Dependent Kinases, or CDKs, are a specific enzyme family that use signals to switch on cell cycle mechanisms.