DNA, RNA, Chromosomes, and Genes


How fast is DNA copied in both prokaryotes and eukaryotes?

The question “Where was the body of King Richard III buried?” has long been a curiosity in England. Historians knew that Richard rode out from Leicester to meet his death on the Bosworth battlefield in August of 1485, ending the Plantagenet reign—but no one knew where his body ended up. Legends told of tossing the body in the river or bringing the body back to town. Still others say the body was claimed by Franciscans and buried hastily near the high altar of their church— and it was at that church where the alleged remains of King Richard were found.

In 2013, several tests were carried out—including radio carbon dating of bone samples and several forensic pathologists determining the cause of death based on the bones. But one clue was the key: comparing the DNA from the leg bone of Canadian Michael Ibsen, believed to be a direct descendant of Richard’s sister Anne. When all the tests came in, the researchers concluded that the bones found at the church site were truly those of King Richard. Alas, King Richard’s lineage apparently stops there, as both Ibsen and his sister (mitochondrial DNA is passed on through the women) have no children.

In prokaryotes, about 1,000 nucleotides can be copied per second; for example, the bacteria E. coli can be copied in about forty minutes. Since the eukaryotic genome is immense compared to the prokaryotic genome, one might think that the eukaryotic DNA replication would take a very long time. However, actual measurements show that the chromosomes in eukaryotes have multiple replication sites per chromosome. Eukaryotic cells can replicate about 500 to 5,000 bases per minute; the actual time to copy the entire genome (collection of genes) would depend on the size of their genome. (For more about prokaryotes and eukaryotes, see the chapter “Cellular Basics.”)


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