David Sadava H Craig Heller Gordon H Orians

  • Slides: 26
Download presentation
David Sadava H. Craig Heller Gordon H. Orians William K. Purves David M. Hillis

David Sadava H. Craig Heller Gordon H. Orians William K. Purves David M. Hillis Biologia. blu B – Le basi molecolari della vita e dell’evoluzione The Genetics of Viruses and Prokaryotes

The Genetics of Viruses and Prokaryotes • How do viruses reproduce and transmit genes?

The Genetics of Viruses and Prokaryotes • How do viruses reproduce and transmit genes? • How do prokaryotes exchange genes? • How is gene expression regulated in prokaryotes?

The Genetics of Viruses and Prokaryotes - How do viruses reproduce and transmit genes?

The Genetics of Viruses and Prokaryotes - How do viruses reproduce and transmit genes? Classification: • genome of DNA or RNA; • nucleic acid is single- or double-stranded; • simple or complex shape; • whether virion is surrounded by a membrane or not; • type of organism it infects; • manner of the infection.

The Genetics of Viruses and Prokaryotes - How do viruses reproduce and transmit genes?

The Genetics of Viruses and Prokaryotes - How do viruses reproduce and transmit genes? Virions come in various shapes

The Genetics of Viruses and Prokaryotes - How do viruses reproduce and transmit genes?

The Genetics of Viruses and Prokaryotes - How do viruses reproduce and transmit genes? Viruses that infect bacteria are called bacteriophage or phage. Phage binds to a receptor on the host cell wall, injects the nucleic acid, then one of two things happens: 1) phage reproduces immediately and kills the host cell - lytic cycle - cell bursts and releases progeny viruses; 2) postpones reproduction by integrating into the host cell’s genome - lysogenic cycle.

The Genetics of Viruses and Prokaryotes - How do viruses reproduce and transmit genes?

The Genetics of Viruses and Prokaryotes - How do viruses reproduce and transmit genes? The lytic and lysogenic cycles of bacteriophage

The Genetics of Viruses and Prokaryotes - How do viruses reproduce and transmit genes?

The Genetics of Viruses and Prokaryotes - How do viruses reproduce and transmit genes? Animal viruses enter cells in several ways: • a naked virion is taken up by endocytosis; • the enveloped virus has glycoproteins that bind to receptors on host cell, also taken in by endocytosis (e. g. , influenza); • the membrane of the host cell and enveloped virus fuse (e. g. , HIV).

The Genetics of Viruses and Prokaryotes - How do viruses reproduce and transmit genes?

The Genetics of Viruses and Prokaryotes - How do viruses reproduce and transmit genes? The reproductive cycle of the influenza virus

The Genetics of Viruses and Prokaryotes - How do viruses reproduce and transmit genes?

The Genetics of Viruses and Prokaryotes - How do viruses reproduce and transmit genes? HIV is a retrovirus, it has reverse transcriptase, which facilitates RNAdirected DNA synthesis. A DNA provirus is produced that is integrated permanently into the host’s genome. When proviral DNA is activated, new virions are produced.

The Genetics of Viruses and Prokaryotes - How do viruses reproduce and transmit genes?

The Genetics of Viruses and Prokaryotes - How do viruses reproduce and transmit genes? The reproductive cycle of the HIV

The Genetics of Viruses and Prokaryotes - How do viruses reproduce and transmit genes?

The Genetics of Viruses and Prokaryotes - How do viruses reproduce and transmit genes? Prokaryotes have several ways of recombining genes: • conjugation; • transformation; • transduction; • plasmids; • transposable elements.

The Genetics of Viruses and Prokaryotes - How do prokaryotes exchange genes?

The Genetics of Viruses and Prokaryotes - How do prokaryotes exchange genes?

The Genetics of Viruses and Prokaryotes - How do prokaryotes exchange genes? Bacterial conjugation

The Genetics of Viruses and Prokaryotes - How do prokaryotes exchange genes? Bacterial conjugation

The Genetics of Viruses and Prokaryotes - How do prokaryotes exchange genes? Recombination following

The Genetics of Viruses and Prokaryotes - How do prokaryotes exchange genes? Recombination following conjugation

The Genetics of Viruses and Prokaryotes - How do prokaryotes exchange genes? Plasmids exist

The Genetics of Viruses and Prokaryotes - How do prokaryotes exchange genes? Plasmids exist independently of the main chromosome. They can be transferred during conjugation. Plasmids don’t need to recombine with the main chromosome.

The Genetics of Viruses and Prokaryotes - How do prokaryotes exchange genes? Gene transfer

The Genetics of Viruses and Prokaryotes - How do prokaryotes exchange genes? Gene transfer by plasmids

The Genetics of Viruses and Prokaryotes - How do prokaryotes exchange genes? Many plasmids

The Genetics of Viruses and Prokaryotes - How do prokaryotes exchange genes? Many plasmids have special genes. Metabolic factors are plasmids with genes for unusual metabolic functions such as breaking down hydrocarbons. Fertility factors (F factors) have genes needed for conjugation; F factor can be transferred during conjugation.

The Genetics of Viruses and Prokaryotes - How do prokaryotes exchange genes? Resistance factors

The Genetics of Viruses and Prokaryotes - How do prokaryotes exchange genes? Resistance factors (R factors or R plasmids) code for proteins that modify or destroy antibiotics. Some provide resistance to heavy metals. R factors have become more abundant in modern times, possibly because of the heavy use of antibiotics. Antibiotic resistance is a serious threat to human health.

The Genetics of Viruses and Prokaryotes - How do prokaryotes exchange genes? Transposable elements:

The Genetics of Viruses and Prokaryotes - How do prokaryotes exchange genes? Transposable elements: DNA sequences that are inserted into new locations Transposon is a longer transposable element (5, 000 base pairs) that carries one or more additional genes. Transposable elements have contributed to the evolution of plasmids.

The Genetics of Viruses and Prokaryotes - How do prokaryotes exchange genes? Transposable elements

The Genetics of Viruses and Prokaryotes - How do prokaryotes exchange genes? Transposable elements and transposons

The Genetics of Viruses and Prokaryotes - How is gene expression regulated in prokaryotes?

The Genetics of Viruses and Prokaryotes - How is gene expression regulated in prokaryotes? Prokaryotes shut down transcription by placing an obstacle - the operator between the promoter and the structural gene. The operator binds to a protein called a repressor-blocks transcription of m. RNA. Operon: the whole unit - promoter, operator, and one or more structural genes. Operon containing genes for lactose metabolism: lac operon.

The Genetics of Viruses and Prokaryotes - How is gene expression regulated in prokaryotes?

The Genetics of Viruses and Prokaryotes - How is gene expression regulated in prokaryotes? The lac Operon of E. coli

The Genetics of Viruses and Prokaryotes - How is gene expression regulated in prokaryotes?

The Genetics of Viruses and Prokaryotes - How is gene expression regulated in prokaryotes? The lac Operon: an inducible system (part 1)

The Genetics of Viruses and Prokaryotes - How is gene expression regulated in prokaryotes?

The Genetics of Viruses and Prokaryotes - How is gene expression regulated in prokaryotes? The lac Operon: an inducible system (part 2)

The Genetics of Viruses and Prokaryotes - How is gene expression regulated in prokaryotes?

The Genetics of Viruses and Prokaryotes - How is gene expression regulated in prokaryotes? The trp Operon: a repressible system (part 1)

The Genetics of Viruses and Prokaryotes - How is gene expression regulated in prokaryotes?

The Genetics of Viruses and Prokaryotes - How is gene expression regulated in prokaryotes? The trp Operon: a repressible system (part 2)