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And can non-fertility factor plasmids be conjugated?
F+ & F+ cross is also possible with a very low level of fertility.
Hi neils, The way you ask your first question is a bit confusing. I am assuming you mean "can a bacterium carrying a fertility plasmid (F+) transfer that fertility plasmid to another bacterium with the same fertility plasmid (also F+)." The simple answer to that question is No. There are many variations of fertility plasmids, but in the classic types you will read about in biology text books the plasmids actually express genes that prevent secondary mating events. However, one exception is if the two F plasmids are from different plasmid families (or what is called in plasmid lingo...incompatibility groups). In this case it is possible that they have different transfer or maintenance mechanisms that will be compatible with each other, and they could be present together in the same cell. For your second question, it is possible for non-fertility factor plasmids to be conjugated. To be transfered all a plasmid needs is a piece of DNA called an "origin of transfer". This piece of DNA is what can be recognized by the transfer machinery that is coded for on the F-plasmid. So if you have the F-plasmid and another plasmid in the same cell that has an origin of transfer, it can be conjugated into another cell just like the F-plasmid. However, if you have a plasmid with the origin of transfer but no F-plasmid in the same cell then it will not be able to be conjugated. There are some more complex cases but this would be the most simple explanation. I would also suggest you look up some references about plasmid incompatibility groups and tri-parental mating. These pieces of info will be helpful to explain some of these issues.
first of all, thanks a lot for helping me, I have been stuck with this question for quite long. Does this mean that F-plasmids also have genes that code for proteins not involved in mating and condjugation is really about the spreading of genes that are on F-plasmids? (I thought before this explenation that there was only one kind of F-plasmid that coded just for mating)
Yes, conjugal plasmids can carry many many types of genes, particularly those for antibiotic resistance. Also, as I said there can be some genes that will make it hard for other plasmids to enter the cell once an F-plasmid gets in there. Of course when you first learn about them we try to keep it simple so we talk about the F-plasmid like it is one specific plasmid, but there are a very wide variety of conjugal plasmids that have lots of interesting properties. If you are very interested in plasmids I would suggest getting your hands on this text book: http://www.amazon.com/Molecular-Genetics-Bacteria-4th-Edition/dp/1555816274 It is by far the best reference I have read that deals with plasmids in bacteria. It can be a little complex, but give it a shot!
okey, I will! thanks again for helping me.
See this [url]https://books.google.co.in/books?id=zE56CAAAQBAJ&pg=RA1-PA150&lpg=RA1-PA150&dq=F%2B+cross+F%2B+bacterium&source=bl&ots=2SrVyNTLBb&sig=kdkwsXGudXFJxAFkzQvjnUDnLis&hl=en&sa=X&ved=0CEoQ6AEwCGoVChMItNi9nfLBxwIVWI6OCh0UrwhO#v=onepage&q=F%2B%20cross%20F%2B%20bacterium&f=false[/url]