Question

4. A) List the similarities and the differences between DNA replication in prokaryotes and eukaryotes. B) Do prokaryotes have telomeres? Explain why do or why don

Answer 1

Similarities between Prokaryotic and Eukaryotic DNA Replication

The steps for DNA replication are generally the same for all prokaryotic and eukaryotic organisms. Unwinding the DNA is accomplished by an enzyme named DNA helicase and manufacturing new DNA strands is orchestrated by enzymes called polymerases. Both types of organisms also follow a pattern called semi-conservative replication. In this pattern, the individual strands of DNA are manufactured in different directions, producing a leading and a lagging strand. Lagging strands are created by the production of small DNA fragments called Okazaki fragments that are eventually joined together. Both types of organisms also begin new DNA strands with a small primer of RNA.

Differences between Prokaryotic and Eukaryotic DNA Replication

Differences between prokaryotic and eukaryotic DNA replication are largely related to contrasts in size and complexity of the DNA and cells of these organisms. The average eukaryotic cell has 25 times more DNA than a prokaryotic cell. In prokaryotic cells, there is only one point of origin, replication occurs in two opposing directions at the same time, and takes place in the cell cytoplasm. Eukaryotic cells on the other hand, have multiple points of origin, and use unidirectional replication within the nucleus of the cell. Prokaryotic cells possess one or two types of polymerases, whereas eukaryotes have four or more. Replication also happens at a much faster rate in prokaryotic cells, than in eukaryotes. Some bacteria take only 40 minutes, while animal cells such as humans may take up to 400 hours. In addition, eukaryotes also have a distinct process for replicating the telomeres at the ends of their chromosomes. With their circular chromosomes, prokaryotes have no ends to synthesize. Lastly, the short replication in prokaryotes occurs almost continuously, but eukaryotic cells only undergo DNA replication during the S-phase of the cell cycle.

Most prokaryotes, lacking this linear arrangement, do not have telomeres. Telomeres compensate for incomplete semi-conservative DNA replication at chromosomal ends.