Ap 18 genetics_of_viruses_and_bacteria

Chapter 18Genetics of Viruses and Bacteria

Viruses:• are much smaller than bacteria•consist of a genome in a protective coat•reproduce only within host cell•use enzymes and ribosomes of host to make more viruses

Lytic cycle:

Lysogenic cycle:

Lytic cycle:Virus destroys host DNA, makes new viruses, digests cell wall

Lysogenic cycle:Virus inserts DNA into host genome (becoming a dormant prophage). Generations later, virus reactivates.

Lytic cycle:

Lysogenic cycle:

prophage

Lysogenic cycle:

Animal Viruses:• are diverse in their means of infection•often have an envelope acquired from cell membrane.

Retroviruses:• made of RNA•use reverse transcriptase to make DNA from RNA template•DNA inserts into host genome as dormant provirus.

Emerging viruses:• usually existing viruses that expand their host territory.

Viroids:•naked RNA

Prions:•infectious proteins•mad cow disease.

Plasmids:•Small rings of DNA with accessory genes

Bacteria

Plasmids:•Small rings of DNA with accessory genes.chromosome

plasmid

Bacteria

Transformation:Bacteria

Transformation:•Bacteria take up naked DNA

Bacteria

Transduction:Bacteria

Transduction:•Phages carry bacterial DNA

Bacteria

Conjugation:Bacteria

Conjugation:•Bacteria “mate” to share DNA

Bacteria

The F-factor gives a bacteria the ability to conjugate

Bacteria

The F-factor gives a bacteria the ability to conjugate. The F-plasmid carries the genes for sex pili.

Bacteria

Hfr cells (high frequency or recombination cells) have the F plasmid incorporated into the chromosome

Bacteria

Hfr cells (high frequency or recombination cells) have the F plasmid incorporated into the chromosome.The F-factor of an Hfr carries other genes along with it.

Bacteria

R-plasmids carry antibiotic resistance.

Bacteria

Transposons are “jumping genes” that can move about in the genome.

Bacteria

Ap 18 genetics_of_viruses_and_bacteria

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