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Genetics_CH5
The Genetics of Bacteria and Their Viruses
| Question | Answer |
|---|---|
| prokaryotes | DNA is not enclosed in a membrane-bound nucleus |
| cyanobacteria | blue-green algae |
| genome of bacteria | a single molecule of double-stranded DNA in the form of a closed circle |
| plasmids | extra DNA elements that are also circles of DNA, but are smaller than the main bacterial genome and they are found in some bacteria in nature (can replicate in the cytoplasm independent of the host chromosome) - nonessential |
| bacteriophages/ phages | specific viruses that can parasitize bacteria |
| properties viruses have in common with other organisms | genetic material can be DNA or RNA, constituting a short "chromosome" |
| viruses are classified as nonliving because | they cannot reproduce alone and must parasitize living cells and use the molecular machinery of these cells |
| bacteria | reproduce asexually by cell growth and division, one cell becoiming two |
| bacteria are useful to study because | they can be cultured in very large numbers because they are so small, and it is possible to detect and study very rare genetic events that are difficult or impossible to study in eukaryotes |
| asexual cell division | DNA is replicated, but the partitioning of th enew copies into daughter cells involves a different mechanism than mitosis |
| conjugation | the contact and fusion of two different cells that results in gene exchange (physical union of bacterial cells) |
| transformation | the process by which a bacterial cell takes up a piece of DNA from the external environment and incorporates this DNA into its own chromosome |
| transduction | the process by which certain phages pick up a piece of DNa from one bacterial cell and inject it into another, where it can be incorporated into a chromosome |
| phage recombination | two phages with different genotypes both infect the same bacterial cell |
| plating | a process in which a small amount of liquid culture can be pipetted onto a petri plate containg solid agar medium and is spread evenly on the surface with a sterile spreader |
| colony | cells that have divided and reach 10^7 cells (visible to the naked eye at this point) |
| cell clones | members of a colony that have a single genetic ancestor |
| prototrophic | bacteria that can grow and divide on minimal medium (wild-type) |
| minimal medium | a substrate containing only inorganic salts, a carbon source for energy, and water |
| auxotrophic | mutant cells that will not grow unless the medium contains one or more specific cellular building lbocks such as adenine, threonine, or biotin |
| resistant mutants | cells that can divide and form colonies in the presence of the inhibitor (such as the antibiotic streptomycin) |
| genetic markers | allow the geneticist to identify individual strains and keep track of genomes and cells in experiments |
| vector | a gene carrier that forms the basis of the gene transfers at the center of modern genetic engineering |
| E. coli | unicellular and grows by simple cell division |
| donor and recipient | parents during conjugation (1 parent seems to transfer some or all of its genome into another cell... transfer is unequal) |
| fertility factor (F) | a hereditary state that gives the donor ability |
| rolling circle replication | a peculiar mechanism in which the donor cell makes a single-stranded copyof itself - the plasmid "rolls," and as it turns, it reels out the single-stranded copy like fishingline |
| pili | projection that initiates contact with a recipient cell |
| Hfr | able to promote a high frequency of recombination (caused when the free F plasmid integrates into the E. coli chromosome) |
| interrupted mating | a procedure in which mating cell pairs are separated using a kitchen blender |
| exconjugants | cells that took part in conjugation |
| origin (O) | a fixed poin on the donor chromosome from which DNA transfer began (aka... the site at which the F plasmid is inserted) |
| terminus | located at the other end of the F factor (opposite the origin) |
| insertion sequences | regions of homology where the F can insert |
| endogenote | complete genomoe (in bacterial recombination) |
| exogenote | incomplete genome (in bacterial recombination) |
| merozygote | stage in which the cell is a partial diploid because it contains 2 copies of one segment of DNA; one copy is part of the endogenote and the other copy is part of the exogenote |
| unselected markers | alleles that are not last on a chromosome |
| F' (F prime) plasmid | an F plasmid carrying bacterical genome DNA |
| R plasmids | vectors that carry resistances and are transferred rapidly on cell conjugation |
| transposon | unique segments of DNA that can move around to different sites in the genome (often contain alleles for antibiotic resistance) |
| transposition | the process of a unique segment of DNA movie around to different sites in a genome |
| transformation | the uptake of fragments of DNA from external medium that is then incorporated into the chromosome and thus permanently changing the genotype of the recipient |
| bacteriophage | bacterial viruses that parasitize and kill bacteria (means "eater of bacteria") |
| phage | a nucleid acid "chromosome" (DNA or RNA) surrounded by a coat of protein molecules |
| lysis | the process of breaking open the bacterial cell wall once a bacteriophage has taken over the machinery of the bacterial cell, turning off the synthesis of bacterial components and redirecting the bacterial sythentic machinery to make phage components |
| phage lysate | the population of phage progeny |
| plaque | clear area on an opaque lawn of bacteria covering a surface of a plate of solid medium |
| plaque morphology | a description of the clear plaque on the lawn |
| host range | a phage phenotype that describes the type of bacteria the phage infected since some bacteria may be resistance to certain stains |
| mixed infection/ double infection | a host is infected with both types of phage genotypes |
| selective system | only the desired rare event can produce a certain visible outcome (growing viruses on certain medium that another virus cannot grow on) |
| screen | a system in which large numbers of individuals are visually scanned to select the rare "needle in the haystack" |
| transduction | the process of a phage picking up bacterial genes and carrying them from one bacterial cell to another |
| virulent phages | those that immediately lyse and kill the host |
| temperate phages | those that can remain in a host cell fo r aperiod without killing it (their DNA either integrates into the hsot chromsome to replicate with it or replicates separately in the cytoplasm, as does a plasmid |
| prophage | a phage integrated into the bacterial genome |
| lysogenic | a description of a bacterium harboring a quiescent phage |
| lysogen | a bacterium harboring a quiescent phage |
| generalized transduction | phages can carry any typed of the bacterial chromosome |
| specialized transduction | phages can carry only certain parts of the bacterial chromosome |
| cotransductants | strains of bacteria that acquire two phenotypes (the greater this frequency, the close two genetic markers must be) |
| zygotic induction | the entry of lambda prophage into the cell immediately triggers the prophage into a lytic cycle |
| lambda insertion | their is a crossover between the circular lambda phage and the circular E. coli chromosome |
| attachment site | a specific site in where the crossover would occur between |
| insertional mutagenisis | another way to zero in on a mutation's position on a known physical map |
Created by:
Nicolekr
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