What describes a plasmid?

Answer 1

a small organelle

a small loop of DNA

a prokaryotic ribosome

a prokaryotic membrane

Answer 2

A piece of DNA transferred by a bacterium
It is a piece of non-reproductive DNA, typically within a bacterium, that can be transferred to other organisms of the same or different species.

Answer 3

See a plasmid as a parasitic DNA molecule (not RNA).
It invades a cell, replicates at the cost of that
cell, and stays with the cell ever after. When the
cell divides, the plasmid replicates too and both
offspring cells will ocntain the plasmid. But in
addition, a replicated plasmid can transform to
another cell, thus reproducing 'independently' of its
original cell. The transfer of plasmid DNA from one
cell to another (or, in vitro, from the medium into a
cell) we call 'transformation'.

Why does the plasmid do this? In order to exist. Cells
try to protect themselves from such invaders, for
instance by producing restriction enzymes which would
cut any foreign incoming DNA. But the plasmids can
protect themselves against that, just as the cell has
to protect itself against its own restriction enzyme
with the correct modification enzymes.

Plasmids also regularly contain genes that the cell
can benefit from. Instead of being a neutral invader,
the plasmid now becomes a profitable extra genetic
moiety. These can be antibiotic resistance genes, or
virulence genes (those are the most common examples
but the variation is much larger). Would you remove
the plasmid completely from the cell ('curing' the
cell), that property (say antibiotic resistance, or
virulence) would then be lost.

But antibiotic resistance genes are not always encoded
on plasmids: there are many mechanisms how a cell can
be resistant to an antibiotic and some are encoded on
the chromosome.

When you would distroy the chromosomal DNA of the
cell, the cell would die. Then the plasmid can also no
longer replicate, since it requires the cell machinery
to do so.

I hope this aNSWERS YOUR QUESTION

Answer 4

A piece of DNA transferred by a bacterium.

-APEX Learning

Answer 5

a small organelle

a small loop of DNA

a prokaryotic ribosome

a prokaryotic membrane

Answer 6

A plasmid is a small circle of bacterial DNA that replicates within the a cell without the need for chromosomal DNA. They are most often found in bacteria.