13.1
How Do Viruses Reproduce and Transmit
Genes? 283
Viruses are not cells 283
Viruses reproduce only with the help
of living cells 284
Bacteriophage reproduce by a lytic
cycle or a lysogenic cycle 284
Animal viruses have diverse reproductive
cycles 287
Many plant viruses spread with the
help of vectors 289
13.2
How Is Gene Expression Regulated in
Viruses? 289
13.3
How Do Prokaryotes Exchange Genes?
290
The reproduction of prokaryotes gives
rise to clones 290
Bacteria have several ways of recombining
their genes 291
Plasmids are extra chromosomes in
bacteria 293
Transposable elements move genes among
plasmids and chromosomes 295
13.4 How Is
Gene Expression Regulated in Prokaryotes?
296
Regulating gene transcription conserves
energy 296
A single promoter can control the
transcription of adjacent genes 296
Operons are units of transcription
in prokaryotes 297
Operator–repressor control induces
transcription in the lac operon 297
Operator–repressor control represses
transcription in the trp operon 298
Protein synthesis can be controlled
by increasing promoter efficiency
299
13.5
What Have We Learned from the Sequencing
of Prokaryotic Genomes? 300
The sequencing of prokaryotic genomes
has many potential benefits 301
Will defining the genes required for
cellular life lead to artificial life?
302
