Question

Group activity 12 (chapter 12) Group #: Names: 1. A phage that is part of a bacterial chromosome is said to show: B) immunity C) conjugation. D) lysogeny E) virulence. 2. Different Hfr strains that originate from the same F-positive strain provide different transfer maps of bacterial genes because: A) the F plasmid inserts at random into the bacterial chromosome. B) the F plasmid replaces some chromosomal segments when it integrates C) insertion of the plasmid causes rearrangements of the D) integration of the F plasmid slows transfer of DNA during conjugation. E) an integrated F plasmid transfers bacterial genes in random order bacterial chromosome. 3. What is an Hfr strain of bacteria? 4. What is a bacterial "addiction system"? 5. What is the function of the vir genes carried by the Ti plasmid?

Answer 1

1. Lysogeny

Life cycles of bacteriophages. During infection a phage attaches to a bacterium and inserts its genetic material into the cell. After that a phage usually follows one of two life cycles, lytic (virulent) or lysogenic (temperate). Lytic phages take over the machinery of the cell to make phage components.

2. option D

3. A high-frequency recombination cell (Hfr cell) (also called an Hfr strain) is a bacterium with a conjugative plasmid (for example, the F-factor) integrated into its chromosomal DNA. The integration of the plasmid into the cell's chromosome is through homologous recombination.

4. To prevent plasmid loss from populations, many plasmids encode plasmid addiction systems (PASs) to kill cells that have lost their plasmids through post-segregational killing effects.