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genetics final
| Question | Answer |
|---|---|
| mutant types of bacteria (2) | nutritional and antibiotic |
| nutritional mutants (2) | prototroph and auxotroph |
| prototroph | can synthesize all essential organic compounds; grows on minimal medium |
| auxotroph | lost ability to synthesize an essential compound; needs supplemented medium to grow |
| antibiotic mutant | resistant/sensitive to specific antibiotics |
| selective media | used to isolate genotypes by limiting nutrients/adding selective agents; only desired mutants/recombs. grow |
| bacterial growth curve (3 phases) | lag, log, stationary |
| lag phase | initial, slow growth/adaptation |
| log phase | exponential growth, rapid cell division |
| stationary phase | growth slows/stops as nutrients deplete/waste grows |
| genetic recombination in bacteria (evidence) | lederberg & tatum, davis u-tube experiment |
| mechanisms of genetic recombination in bacteria (3) | conjugation, transformation, transduction |
| differences from eukaryotic recombination (3) | unidirectional transfer, only part of donor genome is transferred, transferred DNA is incorporated into recipient chromosome via recomb. to be stable (homo. recomb.) |
| conjugation | transfer of genetic material between bacteria through direct cell-to-cell contact, often via a pilus |
| F Factor (Fertility Factor) | a plasmid carrying genes needed for conjugation (pilus formation) |
| F+ cells (donors) | contain F Factor |
| F- cells (recipients) | lack F factor |
| F Factor Mating | (F+)(F-) factor is transferred, recipient becomes F+ |
| process of conjugation | (F+)(F-) results in (2) F+ cells |
| Hfr Strains | high frequency recombination |
| plasmids | extrachromosomal, circular, double stranded, DNA molecules that replicate independently |
| R plasmids | carry genes conferring antibiotic resistance |
| r plasmids contain | RTF (resistance transfer factor) & r-determinants |
| RTF (resistance transfer factor) | genes for plasmid transfer |
| r-determinants | genes for antibiotic resistance (AmpR, TcR) |
| transformation | uptake of free DNA fragments from the environment by a recipient cell and incorporation into its chromosome |
| competence of transformation | physical state allowing a cell to take up DNA |
| cotransformation mapping | genes located close together on chromosome are more likely to be on the same transforming DNA fragment, thus transferred together |
| bacteriophage structure | head, collar, sheath, base plate, tail fibers, |
| phage life cycles (2) | lytic and lysogenic cycle |
| transduction | transfer of bacterial dna from one bacterium to another via a bacteriophage |
| discovery of transduction | Zinder & Lederberg (1950s) - used U-tube with Salmonella, found genetic exchange occurred via a filterable agent (phage) |
| types of transduction (2) | generalized and specialized |
| generalized | During lytic cycle, random fragments of degrading host DNA are mistakenly packaged into phage heads. Any bacterial gene can be transferred. |
| specialized | During excision of a prophage from the host chromosome (lysogenic cycle), imprecise excision takes adjacent bacterial genes along with the phage DNA. Only genes near the prophage integration site are transferred. |
| cotransduction mapping | Similar principle to cotransformation. Closely linked genes can be cotransduced (transferred together in one phage particle). Frequency used to map gene order and distance. |
| phage recombination | Occurs when two different mutant phages co-infect the same host cell. Recombinant phage progeny can be produced. |
| phage mapping | Recombination frequency between phage genes calculated from progeny phenotypes. |
| recombination frequency = | (Total Number of Plaques)(Number of Recombinant Plaques)×100 |
| frequency is proportional to | the genetic distance between the phage genes |
Created by:
user-1948080