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.
The cell cycle. 1  Gap 1 or G1 phase, where the cell grows in size, and checks that everything is OK for it to divide. 2  Synthesis or the S phase, where the cell copies its DNA. 3  Gap 2 or G2 phase, where the cells checks that all its DNA has been correctly copied. 4  Mitosis or M phase, where the cell finally divides in two.