Chapter 5 Flashcards
What class of organism does bacteria belong to?
- prokaryote
What’s a key defining feature of prokaryotes?
- their DNA is not enclosed in a membrane-bound nucleus
What’s unique about bacteria’s DNA?
- genome is a single molecule of double-stranded DNA in a closed circle
- contains extra DNA elements called plasmids
What are plasmids?
- DNA circles that are much smaller than the main bacterial genome
What are viruses regarded as, even though they are similar to organisms in some aspects?
- nonliving, because they don’t have a metabolism on their own
How does bacteria reproduce, generally?
- asexually, cell growth and division
T/F: bacteria (and other prokaryotes) never reproduce sexually
- false
- they undergo both sexual and asexual reproduction
Why are bacteria a model organism for genetic studies?
- fast-dividing
- take up little space
- reproduce asexually until nutrients are exhausted or toxic waste products accumulate
can be cultured on liquid or solid mediums with only basic nutrients provided
When can bacteria be seen with the naked eye in a colony?
- when it reaches a population of 10^7 cells
What is one thing that is needed for bacteria to exchange genetic information?
- physical contact
- aka conjugation
What was different with the bacterial genetic exchange that is not seen with eukaryotic crosses?
- one parent transferred some or all of its genome into another cell
- one cell was acting as a donor and one cell was acting as a recipient
What does F+ mean?
- a strain of bacteria that carry fertility factor (F) can donate to recipient strains
What does F- mean?
- a strain of bacteria that does not carry fertility factor (F) cannot donate but can receive from donor strains
What is F?
- fertility factor
- a plasmid
What does the F plasmid do?
- directs the synthesis of of pili
- projections that initiate contact with the recipient
- draw it closer
How does the F in DNA donate itself to the recipient?
- makes a single stranded version of itself through rolling
- passes through a pore of the recipient cell where the other strand is synthesized, making a double helix
T/F: a copy of F remains with the donor
- true
- one stays in the donor, one is in the recipient
What does Hfr stand for?
- high frequency of recombination
What happen in Hfr and F- crosses? What makes them different from F- and F+ crosses?
- virtually none of the F- became F+ or Hfr
- with +x-, most F- become F+
Define prokaryotes
-
Define viruses
-
Define donor
-
Define bacteriophages
-
Define phages
-
Define horizontal transmission
-
Define vertical transmission
-
Define phage recombination
-
Define plating
-
Define colony
-
Define cell clones
-
Define prototrophic
-
Define minimal medium
-
Define auxotrophic
-
Define resistant mutants
-
Define genetic markers
-
Define conjugation
-
Define fertility factor F
-
Define F+
-
Define F-
-
Define plasmid
-
Define circle replicaiton
-
Define rolling
-
Define Hfr
-
Define recipient
-
Define interrupted mating
-
Define exconjugants
-
Define origin (O)
-
Define terminus
-
Define endogenate
-
Define exogenate
-
Define merozygote
-
Define unselected marker
-
Define F’ plasmid
-
Define R plasmid
-
Define transformation
-
Define double transformation
-
Define lysis
-
Define lysate
-
Define plaque
-
Define mixed infection
-
Define double infection
-
Define selective system
-
Define screen
-
Define transduction
-
Define virulent phages
-
Define temperate phages
-
Define prophage
-
Define lysogenic
-
Define lysogen
-
Define circle replicaiton
-
Define generalized transduction
-
Define cotransductants
-
Define specialized transduction
-
Define zygotic induction
-
Define lambda (h) insertion
-
Define lambda (h) attachment site
-
Define auxotroph
- a strain of microorganisms that will proliferate only when the medium is supplemented with a specific substance not required by wild-type organisms
Define bacteriophage
- aka a phage
- a virus that infects bacteria
Define cell clome
- members of a clony that have a single genetic ancestor
Define colony
- a visible clone of cells
Define conjugation
- the union of 2 bacterial cells during which chromosomal material is transferred from the donor to the recipient cell
Define lambda attachement site
- where the lambda prophage inserts into the E.coli chromosome
Define donor
- bacterial cell used in studies of unidirectional DNA transmission to other cells
- ex in Hfr in conjugation and pahge source in tranduction
Define double (mixed) reaction
- infection of bacterium with 2 genetically different phages
Define double transformation
- simultaneous transformation by 2 different donor markers
Define endogenote
- a complete chromosome
Define exogenote
- a chromosome fragment
Define F+ (donor)
- in E.coli a cell having a fee ferrtility factor
- a male cell
Define F- (receipietn)
- in E.coli a cell having no fertility factor
- a female cell
Define F’ plasmid
- a fertility factor into which a part of the bacterial chromosome has been incorporated
Define fertility factor
- a bacterial episome whose presence confers donor ability
- maleness
Define generalized transduction
- the ability of certain phages to tranduce any gene in the bacterial chromosome
Define genetic marker
- an allele used as an experimental probe to keep track of an individual organism, a tissue, a cell, a nucleus, a chromosome or a gene
Define Hfr
- high frequency of recombination
- In E.coli a cell having its fertility factor integrated into the bacterial chromosome
- a donor male cell
Define horizontal transmission
-inheritance of DNA from another member of the same generation
Define insertional mutagensis
- the situation whene a mutation arises by the interruption of a gene by foreign DNA, such as from a trangenic construct or a transposable element
Define interrupted mating
- a technique used to map bacterial genes by determining the sequence in which donor genes enter recipient cells
Define lysate
- population of phage progeny
Define lysis
- the rupture and death of a bacterial cell on release of phage progeny
Define lysogen (lysogenic bacterium)
- a bacterial cell containing an inert prophage integrated into, and that is replicated with the host, chromosome
Define merozygote
- a partly diploid E.coli cell formed from a complete chromosome (the endogenote) plus a fragment (exogenote)
Define minimal medium
- medium containing only inorganic salts, a carbon source and water
Define mixed (double infection)
- the infection of bacterial culture with 2 different phage genotypes
Define origin (O)
- aka origin of replication
- the point of a specific sequence at which DNA replication
Define phage recombination
- the production of recombinant ohage genotypes as a result of doubly infecting a bacterial cell with different “parental” phage genotypes
Define plaque
- a clear area on a bacterial lawn, left by lysis of the bacteria through progressive infections by a phage and its descendants
Define plasmid
- an autonomously replicating extrachromosomal DNA molecule
Define plating
- spreading the cells of a microorganism (bacteria, fungi) on a dish of nutritive medium to allow cell to form a visible colony
Define prokaryote
- an organism composed of a prokaryotic cell, such as a bacterium or blue-green alga
Define prophage
- a phage “chromosome” inserted as part of the linear structure of the DNA chromosome of a bacterium
Define prototroph
- a strain of organisms that will proliferate on minimal medium
Define R plasmid
- a plasmid containing one or several transposons taht bear resistance genes
Define recipient
- the bacterial cell that receives DNA in a unilateral transfer between cells
- ex: F- in conjugation or the transduced cell in phage-mediated transduction
Define resistant mutant
- a mutant that can grow in a normally toxic environment
Define rolling circle replication
- a mode of replication used by some circular DNA molecules in bacteria (like plasmids) in which the circle seems to rotate as it reels out one continuous leading strand
Define screen
- a mutagenesis procedure in which essentially all mutagenized progeny are recovered and are individually evaluated for mutant phenotype
- often teh desired phenotype is marked in some way to enable its detection
Define specialized transduction
- the situation in which a particular phage will transduce only specific regions of the bacterial chromosome
Define temperate phage
- a phage tha t can become a prophage
Define terminus
- the end represented by the last added monomer in the unidirectional synthesis of a polymer such as RNA or a polypeptide
Define transduction
- the movement of genes froma bacterial donor toa bacterial recipient with a phage as the vector
Define transformation
- the directed modification of a genome by the external application of DNA from a cell of different genotype
Define unselected marker
- in a bacterial recombinant experiment, an allele is scored in progeny for the frequency of its cosegregation with a linked selected allele
Define vertical transmission
- inheritance of DNA from a member of a previous generation
Define virulent phage
- a phage that cannot become a prophage
Define virus
- a particle consisting of nucleic acid and protein that must infect a living cell to replicate and reproduce
Define zygotic induction
- the sudden release of a lysogenic phage from a Hfr chromosome when the prophage enters the F- cell followed by the subsequent lysis of the recipient cell
