Plasmids - A Few Questions (Jan/22/2006 )
Can someone explain to me how plasmid DNA is similar to the DNA found in choromosomes and how plasmid DNA is different from the DNA found in chromosomes?
Also, what would be the advantages of inserting into a plasmid a gene with a highly visible phenotype?
A lux gene enables some organisms to make a chemical that glows in the dark. How could this gene be used to identify the bacterial colonies on a cultural plate that have actually picked up the plasmid?
Thank you in advance!
LODYH...?
is this your homework?
I actually used to possess a plasmid from E.P. Greenberg's lab (pHV200, I believe) that contained the lux operon and would glow in the dark in transformed e. coli cells. That thing was sweet! You could create glowing smiley faces and stuff in LB agar. Zero percent research utility, 100% amusement factor.
As for your questions:
Q2: It makes screening for the desired plasmid much easier and less time consuming. (hence the beta gal/xgal approach).
Q3: The colonies that glow are the ones that have picked up the plasmid.
-Matt
is this your homework?
sorry...but what does LODYH stand for??
and no....it isn't exactly homework...we have a short answer quiz on this stuff...and my teacher gave us hints (like wat we should study) and so i looked for the answers in the book and I couldn't even find the most obvious answers (for Q1) and Q2/Q3 were just confusing me because we didn't really go into depth and 'application' with this stuff....
Thank you, Matt for your help! much appreciated!!
That sounds like an interesting lab...we didn't get to any yet sadly. But Thanks Again!! first and foremost:
with that out of the way,
1. Plasmids are relatively small, double-stranded, closed-circular DNA molecules that exist apart from the chromosomes of their hosts, and is usually located in the cytoplasm. Naturally occuring plasmids carry one or more genes, the most notable examples are for resistance to certain antibiotics or for the direct synthesis of enzymes that aid in the production of poisons or antibiotics (bacteria).Plasmids contain a origion of replication (aka origin). That allows the plasmid to multiply within and almost independly of its host.
Chromosomes are what happens with the DNA is packaged into one or more large marcomoluces.
It is a ver long, continuous piece of DNA which contains many genes, regulatory elemens, and intervening nucleotide sequences. The stand of DNA (within the nucleus) is wraped around histones. During mitosis the chromosomes are condensed and a spindle of microtubles is formed. etc etc etc
so, plasmids: small, chromosomes: big.
plasmid: small number of genes, chromosomes: big number of genes
Plasmid: in cytoplasm chromosomes: in nucleus
Plasmid: dsDNA, chromosome: dsDNA
etc
go through and make a list, you can do this by reading and taking notes at the same time.
2. Plasmids are used as cloning vectors. Something that is quite desirable is knowing that they were successfully shoved inside a bacteria or a cell. look up things like Luciferase or CAT (chloramphenicol transferase sp?). It'll explain a whole lot more.
3. Lux (luciferase) is the thing that makes fireflies glow. Think this through. If the cells glow, they've got the gene.
sorry if i'm comming off as a pain the arse, want to help, but severely sunburnt and thus quite cranky.
Lazybones, Oughta Do Your Homework