DNA replication in prokaryotes and eukaryotes

Compare the structure of genomes and replication initiation factors in DNA replication in prokaryotes and eukaryotes.

Pro: Have a single point of origin due to their small genomes, DNA is circular. OriC is the initation factor

Euk: Have multiple points of origin due to the larger genome, genome is linear. Orc, Cdc6 and Cdt1 are the initiation factors

Compare the DNA unwinding in DNA replication in prokaryotes and eukaryotes.

Helicase is loaded on by a loader. Helicase unwinds the complementary strands of DNA, breaking hydrogen bonds between them this produces single stranded DNA. Single stranded binding proteins bind to stabilise single stranded DNA and prevent reannealing. Topoisomerase may run ahead of helicase to reduce strain

Pro: Helicase loader is DNAC. Helicase is DNAB, SSBPs are called SSBPs. Topoisomerase 1 cuts one strand of DNA, DNA grease introduces negative supercoils. This aids compaction

Euk: Helicase loader is Cdc6+Cdt1. Helicase is the MCM complex, SSBPs are Replication factor A. Uses Topoisomerase 1 +2 (cuts both strands), no gyros used as DNA is already organised

Describe priming of DNA in DNA replication in prokaryotes and eukaryotes

A primase synthesises short primers to act as start sites, these supply a 3’OH

Pro: DNA G adds the primers

Euk: DNA polymerase a adds primers

Compare the stage of elongation in DNA replication in prokaryotes and eukaryotes.

DNA polymerase is loaded on and held on too. Polymerase binds the correct, complementary nucleotides in, moves in the 5’ to 3’ direction. Forms Okazaki fragments on the lag

Pro: Polymerase loader is the gamma complex, B clamp holds on. Polymerase 3 extends

Euk: Polymerase loader is the Replication factor C, PCNA (proliferating cell nuclear antigen) holds DNA polymerase onto DNA. Polymerase delta extends lagging strand, polymerase epsilon extends leading strand

Compare the DNA ligases in DNA replication in prokaryotes and eukaryotes.

Seal nicks between strands

Pro: DNA ligase

Euk: DNA ligase 1

Compare the primer removal in DNA replication in prokaryotes and eukaryotes.

Pro: DNA polymerase 1 removes primers

Euk: RNaseH and FEN1 remove primers

Compare the termination in DNA replication in prokaryotes and eukaryotes.

Pro: Tus protein binds termination sites

Euk: No specific termination sites

Compare the use of telomerase in DNA replication in prokaryotes and eukaryotes.

Pro: Not required due to circular nature of chromsomes

Euk: Required to maintain telomeres and prevent degradation

Compare stages of the cell cycle DNA replication happens in in prokaryotes and eukaryotes.

Pro: Continuous replication

Euk: Occurs only during S phase