Single replication bubbles

Replication starts at a single origin, is bi-directional and semi-conservative. Each replication bubble (or eye) consists of two replication forks. 

Eukaryotes tend to have much more DNAthan prokaryotes. Therefore, to speed the process of replication it occnrs in multiple replication bubbles (Fig. 63.3). Within each bubble, DNA replication occnrs at two replication forks. However, in prokaryotes there is only a single replication bubble (Fig. 63.4). In both prokaryotes and enkaryotes, the consensus sequence at an origin of replication varies but all have a high content of A and T, which facilitates separation of the strands. Remember that A=T bonds (two hydrogen bonds) are more easily separated than CsG bonds (three hydrogen bonds). 

Multiple replication bubbles (Fig. 63.3) Single replication bubble (Fig. 63.4)... 

Replication starts by the separation of the strands of DNA and the formation of a local bubble at a specific DNA site called the origin of replication (ori). A helicase enzyme uses energy from ATP hydrolysis to effect this action. Single-strand DNA binding proteins stabilize the strands during the subsequent steps. The original DNA strands will function as the templates that will direct synthesis of the complementary strands. A nucleotide on the template strand will determine which deoxyribonucleotide (dNTP) will be incorporated in the newly synthesized strand. This replica-... 

Fig 11.14 Single bubble for DNA Replication in Prokaryotic Chromosomes Requirements for DNA Synthesis... 

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