Rolling Circle Mechanisms of Replication

Is all DNA replicated in the same manner? DNA is synthesized by the enzyme DNA polymerase. This enzyme is common to all cellular organisms. However DNA is organized differently in different organisms. In eukaryotes DNA is organized into chromosomes, each of which is a single linear piece of DNA. The number of chromosomes is highly variable in different eukaryotes. In prokaryotes the DNA is typically organized into a single continuous loop of DNA. However prokaryotes may also contain plasmids which are smaller pieces of circular DNA which are obtained from other bacteria during conjugation. The different organization of different types of DNA requires slightly different methods of replication.

View the animation below, then complete the quiz to test your knowledge of the concept.


1	The free 3'OH end is

		A)	made into a tail of single-stranded DNA that extends from the circle
		B)	converted to double-stranded DNA by RNA primer
		C)	unaffected by the replication process
		D)	extended by DNA polymerase

2	The 5' end

		A)	is extended by DNA polymerase
		B)	forms a tail of single-stranded DNA that extends from the circle
		C)	is double-stranded DNA that replicates into two double-stranded DNA sets
		D)	remains unchanged

3	In the rolling circle method of replication

		A)	the 5' tail of DNA is nicked
		B)	RNA is nicked
		C)	one strand of DNA in the circle is nicked
		D)	both strands of DNA in the circle are nicked

4	The rolling circle method of reproduction is used in the reproduction of certain viruses.

		A)	True
		B)	False

5	The 5' end with the single-stranded DNA tail is converted to double-stranded DNA using RNA primers.

		A)	True
		B)	False

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