Describe the structure of a plasmid.

Question

Accepted Answer

All right, everybody. Our next question says which of the following statements about the structure of DNA plasmids are correct. And then we have four different statements labeled one through four. And our answer choices A through D are different combinations of these. So A is 12 and three, B, 13 and four, C 23 and four or D 123 and four. So given that we have possibilities that all of these may be correct, we need to look through them and decide what our correct combination is. So let's start with statement. Number one plasmids are circular DNA molecules that replicate independently of the chromosomal DNA. Well, this is correct. They are circular pieces of DNA and they can replicate on their own even when the chromosomal DNA is not currently replicating. So choice one is correct. So we can go ahead and eliminate, see, since that doesn't have one in it. Now, let's look at our next statement. We have statement, two plasmas are found exclusively in eukaryotic cells. Well, this one is definitely incorrect plasmas are found primarily in prokaryotic cells. Rather, there are some yeast cells that have plasmid like structures So we won't say exclusively but almost all plasmids we'd see only in a prokaryotic cell. So statement two is incorrect. So we can eliminate choice D in which all of them are correct. So let's move on to statement, three plasmids can be transferred between bacteria through a process called conjugation. And this is correct. That's a process of horizontal gene transfer where the cells are actually physically connected by a structure called a pili. And the DNA can be transferred through that from one cell to the other. So number three is correct. So a, well, A and B both have three in them. So that doesn't help us. And then finally, statement, four plasmids include a replication origin that allows them to replicate independently. Well, we already said that they replicate independently. But this statement is correct and that is this replication origin that allows them to do that. So the cell, the whole cell as a whole doesn't need to be going through the process of replication. They can start up themselves since they have their own replication origin. So statement four is correct. So our answer is choice B statements one, three and four are our correct statements. While statement two is incorrect. See you in the next video.

Describe the structure of a plasmid.

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Key Concepts

Plasmid Structure

Origin of Replication (ori)

Selectable Markers