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Chap 11 - Genetics

Genetics of Bacteria

QuestionAnswer
a mutation is a heritable change in a DNA Sequence that can lead to a change in the organisms phenotype
the visible change in an organism is a change in (phenotype/genotype), however the genetic change in an organism is a change in (phenotype/genotype) the visible change in an organism is a change in PHENOTYPE; however the genetic change in an organism is GENOTYPE
the wildtype strain refers to the strain that is typically isolated from nature, it can also refer to a single gene
a ______________ is a cell/virus that is derived from the wild type that carries a change in genetic sequence mutant is a cell/virus that is genetically different from the wild type
a mutant (can/cannot) be obtained from a parental strain which have been previously derived from the wild-type a mutant CAN be derived from a parental strain which was previously derived from the wild type
explain why a mutant may not differ from the wild-type in phenotype the genotype might be different in a mutant. however, the gene might still code for the same protein. Therefore, producing the same phenotype
in Microbiology, how his genotype represented italicized three-lowercase letters and a capital letter for the gene (i.e. hisC)
observe these examples: hisC1 and hisC2. in the examples, what do the numbers mean in the examples hisC1 and hisC2, the numbers refer to the order of isolation in the mutations
give an example of a bacterial phenotype for the hisC genotype. His- or His+
how is phenotype usually represented in bacteria + or - (example: (protein)+ or (protein)-)
(selectable/nonselectable) mutations confer an advantage SELECTABLE mutation confer an advantage
under certain environmental conditions, the later generations will outgrow and replace the parental/wild type strains , is an example of ______________________ selectable mutations
give some examples of selectable mutations antibiotic resistant bacteria
selectable mutations are powerful tools because mutants are easy to select
(selectable/nonselectable) mutations do not confer an advantage even though they may lead to a phenotypic change NONSELECTABLE mutations do not confer an advantage even though they may lead to a phenotypic change
color loss in a pigmented organism would be an example of a (selectable/nonselectable) mutation. color loss would be a NONSELECTABLE phenotypic change
what is the purpose of replica plating screening for nutritionally defective mutants
this process includes 1) transferring colonies from a master plate, 2) seeing which colonies can/cannot grow, and 3) picking and purifying the colonies that do grow replica plating
if a colony is unable to grow on a replica plate, this means that the colony is lacking a curtain nutrient or has a particular mutation
an auxotroph is _______________ an additional nutritional requirement that is needed for growth...usually this nutrient is needs to be added to the petri dish
the parental strain is called a _________________ prototroph
___________________ mutation is a mutation that occurs without external intervention. Most result from occasional errors by DNA polymerase during replication Spontaneous mutations
a _____________________ mutation is made environmentally and deliberately. induced mutations
a(n) (induced/spontaneous) mutation can result from exposure to natural radiation or chemicals INDUCED mutations can occur from natural radiation or chemicals
what is a point mutation a mutation that only involves one nucleotide base pair
point mutations have the ability to ... change a single amino acid, lead to an incomplete chain, or might not have any effect at all
nonsense, missense, and silent mutations are all the result of _______________________ silent, missense, and nonsense mutations are all the result of POINT MUTATIONS
what is a silent mutation a point mutation that does not affect the sequence of an amino acid in a polypeptide chain...there for the phenotype is not changed
the silent mutation is always a ______________________ codon third base
__________ is a mutation that changes the sequence of an amino acid in a poly peptide chain missense mutation changes the amino acid in a sequence of a polypeptide chain.
how could a missense mutation affect the amino acid if the amino acid is in a critical location (i.e. active site) then the activity of the protein could be altered.
(all/not all) missense mutations can lead to dysfunction NOT ALL missense mutations lead to disfunction
what is a nonsense mutation nonsense mutation leads to a stop codon too early in the polypeptide
what typically happens as a result of a nonsense mutation the polypeptide is incomplete/truncated and will not have normal activity
transition base pair substitution is ________________ switching a purine for the other purine; or a pyrimidine for the other pyrimidine
what is a transversion base pair substitution switching a purine for a pyrimidine and vice versa.
what leads to a frameshift mutation either the deletion of a base pair or the insertion of a base pair
the deletion/insertion of _____________ base pairs leads to another amino acid being deleted/inserted three
generally speaking, what does a frameshift do to the genome frameshifts usually scramble the entire polypeptide sequence up/downstream
insertions/deletions can result in the gain/loss of ________________ to ________________________ of base pairs hundreds to thousands
frameshift mutations often result in ___________________ frameshift mutations often result in COMPLETE LOSS of gene functions
what might cause a frameshift mutation errors during the genetic recombination
large number of base pair insertions may be due to ______________________ (DNA being inserted into other DNA) transposable elements
mutation rates depend on _______________ the frequency of DNA changes and the efficiency of DNA repair
what is a reversion a point mutation that is typically reversible
what is a revertant a strain in which the original phenotype is restored
a __________________ revertant is a mutation at the same site as the original mutation same-site revertant
a _____________ revertant restores the original sequence true revertant
the ______________ revertant is a mutation that is in a different site but restores the DNA wild type second - site revertant
a second - site revertant works only if they have ______________________ compensating for the original effect suppressor mutations
where can second-site mutations occur somewhere elseo on the same gene, on another gene but restores function in the original gene, on another gene and the other gene starts producing the needed protein.
what is the relative frequency in errors during DNA replication in microorganisms 1/10^6 to 1/10^7 per kilobase
the relative error frequency in a single gene is (the same/higher/lower) than the error frequency of DNA the error frequency for a typical gene is about THE SAME as DNA replication errors
(eukaryotes/prokaryotes) have about 10-fold lower error rates than (eukaryotes/prokaryotes) EUKARYOTES have about 10-fold lower error rates than PROKARYOTES
why do RNA viruses have the highest rates of errors RNA viruses have less proofreading and lack RNA repair mechanisms
DNA viruses have (higher/lower) error rates than RNA viruses but (higher/lower) error rates than prokaryotes DNA viruses have LOWER error rates than RNA viruses but HIGHER error rates than prokaryotes
single base errors are more likely to lead to (missense/nonsense) mutations because most substitutions encode for amino acids single base errors are more likely to results in MISSENSE mutations
list the three types of point mutations from most frequent to least frequent missense mutations > silent mutations > nonsense mutations
one can (increase/decrease) the pool of mutations in DNA by treating with mutagenic agents, or under conditions of high stress mutagenic agents/high stress INCREASES the pool of mutations
__________________________ is the physical exchange of DNA between genetic elements recombination is the physical exchange of DNA between genetic elements
what is homologous recombination a process that results in genetic exchange between homologous (closely related) DNA from two different sources
___________________ drives the "crossing over" seen in classical genetics during meiosis homologous recombination drives the "crossing over" in classical genetics
________________ is an essential enzyme, identified in all Bacteria, Archaea, and most Eukarya RecA
in homologous recombination, ______________________ nicks one DNA strand of the donor molecule endonuclease
the _________________ separates the nicked strand from the other strand helicase
this protein binds to a single-stranded segment and to RecA single-strand binding protien
starting with endonuclease, name the proteins that assist in homologous recombination in order, briefly describe what they do endonuclease (nicks one strand), helicase (separates the two strands), and single-strand binding protein (keeps strands separate and bound to RecA)
______________ is when base pairing displaces other strand of recipient DNA strand invasion
strand invasion creates.... recombination intermediates with heteroduplex regions where each strand stand is from a different chromosome
in homologous recombination, how do the participating DNA sequences generated a new genotype the homologous sequences must be related but distinct (i.e. diploid eukaryotic cell DNA)
in bacteria genetic recombination can occur after...... transformation, transduction, or conjucation
how do you detect the exchange of DNA in recombinant cells look at the phenotype, usually the recombinant cells phenotypically differ from both parents
in transformation, transduction, or conjugation, (the entire/only part) of the donor chromosome enters the recipient cell in genetic recombination ONLY PART of the donor chromosome enters the recipient cell
in order for the donor DNA to be lost, recombination must take place in..... the recipient chromosome
what is a merodiploid strain a bacteria that carries two copies of a particular chromosomal segment
in a merodiploid strain, usually one copy is on the _________________ and the other copy is on a ___________________ chromosome; plasmid (or phage)
what is complementation when a functional wild-type supplied by the plasmid/bacteriophage; there for restoring the wild-type phenotype
________________________: the genetic transfer process by which FREE DNA is incorporated into a recipient cell and brings about genetic change Transformation
what is a competent cell a cell that can take in free DNA and be transformed when this DNA is genetically determined
in naturally transformable bacteria, competence is regulated, __________________________ uptake and process DNA competence-specific proteins
what normally regulates transformation in bacteria quorum sensing (a regulatory system that controls gene expression based on cell density)
high-efficiency natural transformation is (common/rare) in Bacteria high-efficiency natural transformation is RARE in Bacteria
in order to make cells more highly competent ... specific procedures must be implemented
___________________ : when electricity can be used to force cells to take up DNA electroporation
natural transformation starts with ________________________ that becomes irreversible reversible DNA binding
in competent cells, linear DNA is first bound by ______________________ similar to a pilus DNA-binding protien
when a double stranded DNA fragment is taken in and is added to the chromosome..... a nuclease degrades one strand, and the other strand is taken in
________________________ binds and protects new (imported) DNA during transformation competence-specific protiens
what protein integrates new DNA into existing DNA during transformation RecA integrates newly imported DNA during transformation
what happens to a double stranded DNA during transformation that becomes a plasmid the DNA must remain double stranded and circular
___________________: is the transfer of DNA from one cell to another by a bacteriophage transduction
name the two types of transduction generalized transduction and specialized transduction
explain what generalized transduction is the DNA from any portion of the host genome is packaged inside the virion
in ____________________ transduction, the donor genes cannot replicate independently and they will be lost without recombination generalized transduction
what is specialized transduction DNA from a specific regions of the host chromosome is integrated direction into the virus genome
during specialized transduction, when may DNA be integrated lysogeny or homologous recombination
give some examples of bacteria with multiple-antibotic resistance genes E. coli, Salmonella, Shinga-like toxins (in E. coli), virulence factors in Vibrio cholerae, photosythetic cyanobacteria
in generalized transduction (virtually any/only specific) genes can be transferred to the transductant VIRTUALLY ANY
what is a transducing particle a virion that is full of the hosts DNA
transducing particles are (effective/defective) transducing particles are defective and cannot lead to viral infections
what happens to transducing particles during lysis transducing particles are released along with normal virions
(generalized/specialized) transduction is extremely efficient SPECIALIZED transduction is extremely efficient
T phage genome is integrated at a specific cite is an example of (specialized/generalized) transduction T Phages are examples of Specialized Transduction
in what type of transduction is viral replication under the control of bacterial host chromosome in specialized transduction and lysogeny, the viral replication is under the control of the bacterial host
(Not a Question...just information) Upon induction, viral DNA sometimes excises incorrectly and takes adjacent host genes along with it
(not question... just information) There is a limit to the amount of host DNA that can replace Phage DNA, but helper phages can assist
what is phage conversion the alteration of the phenotype of a host cell by lisogenization
(not a question) prophage from normal, nondetective temperate infection becomes immune to further infection by same phage
some bacteria are only virulent if they possess a ________________ - which usually carries a toxin specific prophage
manny natural lysogens have been found, suggesting.... this is an essential process for survival
a GTA is a gene transfer agent
what is a gene transfer agent a defective bacteriophage that transfers DNA between prokaryotic cells
a gene transfer agent results from prokaryotes hijacking deflective viruses, specifically for the purpose of DNA exchange
this item contains small random pieces of host DNA, do not contain genes encoding their own production, and do not produce viral plaques gene transfer agents
why might have gene transfer agents have evolved as a mechanism for protected gene dispersion
_______________________: is the horizontal gene transfer that requires cell-to-cell contact conjucation (mating)
conjucation is (chromosome/plasmid) encoded conjugation is plasmid encoded (F Plasimd)
conjugation occurs between two closely related or distantly related cells
what is the difference between the donor and the recipient cell in conjugation the donor cell contains the plasmid and the recipient does not contain the plasmid
(t/f) during conjugation, only the plasmid may be mobilized wrong (false), other plasmids or chromosomes may be transferred as well
F plasmids contains _____________________ that allows the plasmid to integrate into the host chromosome transposable elements
the __________ gene on the F plasmid encodes transfer functions (i.e. synthesis of sex pilus and a type IV secretion system) tra gene
during conjugation DNA is synthesized via the __________________ rolling circle replication
the F plasmid is an _____________, meaning it can integrate into host chrommosomes episome
the cell processing a nonintegrated F plasmid is called a F+
cells processing an integrated F Plasmid are called Hfr (high frequency recombination) cells
what are the three distinct abilities that results from a cell having an F plasmid ability to synthesize and F pilus, mibilization of DNA transfer to another cell, alteration of surface receptors so that a cell can no longer be a conjugation recipient
Created by: kandriot