SINGLE MOLECULE ANALYSIS OF GENOME REPLICATION.

All cells contain a complete copy of the organism's DNA, the genetic blueprint of life, packaged into discrete units called chromosomes. Since new cells need a copy of the genetic material, the chromosomes must be completely and accurately replicated before the cell can divide. Our research aims to determine how cells ensure that the replication of each chromosome is completed before cell division. Our experimental data have revealed the average pattern of chromosome replication in populations of millions of cells - that is the regions that are replicated first, second and so on. However, in preliminary data we have discovered that individual cells do not replicate their chromosomes with this 'average' pattern; the pattern of DNA replication in single cells is hidden by the population average. Consequently rare problems during DNA replication, including delays in completing replication, cannot currently be readily detected. Therefore, we are developing novel methods to directly measure DNA replication in single molecules. In one approach, we are using a transformative single-molecule sequencing technology to detect the pattern of DNA replication in thousands of long molecules. In addition, we will make use of recent advances in imaging technologies to directly visualise DNA replication in whole chromosomes. These complementary approaches will, for the first time, reveal the pattern of DNA replication on individual chromosomes. This is important because a single DNA replication error on one chromosome in a single cell division can give rise to genomic disorders, including cancer.