Bio1151b
Chapter
18
The Genetics of Viruses and Bacteria
Prokaryotes
and their viruses (
or phages) are
smaller
and simpler then eukaryotes.
Viruses
are intracellular
parasites
and can reproduce only within
cells, using the host's enzymes, ribosomes, and other molecules to synthesize progeny
viruses.
Phages go through two alternative
mechanisms: the
cycle
of a virulent
phage
and the
cycle
of a temperate
phage.
Animal
viruses
include
RNA
viruses, some of which are
use such as
HIV
that
contain
their own
transcriptase.
Bacterial cells divide by
fission,
an asexual process that produces two genetically identical cells.
Genetic recombination in bacteria occurs in three processes:
,
, and
.
Transformation
is the alteration of a bacterial cell's DNA by the uptake of naked, foreign
from the surrounding environment.
Transduction
is the transfer of bacterial
from one host cell to another through
.
Conjugation
is the direct transfer of genetic material between bacterial cells joined by sex
.
Bacterial genes are often clustered into
and regulated by a
repressible
or
inducible
("on-off" switch) and a
that binds RNA
polymerase.
The
lac
operon is also subject to
positive
control by an
such as catabolite activator
protein
working with the regulatory molecule cyclic
AMP.
Summary.