DNA replication. Coloured transmission electron micrograph (TEM) of human DNA (deoxyribonucleic acid, orange strands) from a HeLa cancer cell, showing a stage of DNA replication. At centre is a replication 'bubble', where the DNA has unwound into two single strands. Normally, DNA consists of two tightly wound spiral strands. During the process of replication, a 'bubble' region forms which enlarges to form a Y-shaped molecule termed a replication fork. It is here that daughter strands form as the parent DNA acts as a template for the construction of a new matching strand. In this way the sequence of bases (or genetic information) along the DNA molecule is replicated.