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58 Cards in this Set
- Front
- Back
What is a mutation?
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-heritable change in DNA sequence
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What is a mutant?
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-a strain containing a mutation
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What is a phenotype?
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-an observable property of a strain; a mutation may or may not affect a phenotype
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What is a genotype?
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-precise genetic composition of an organism; a mutation affects genotype
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What does haploid mean?
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-one set of genes/chromosomes (genome)
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What does diploid mean?
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-contain two set of genes/chromosomes
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What is an allele?
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-alternative forms (mutations) of a single gene
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What does heterozygous mean?
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-two alleles of the same gene are different in a diploid
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What does homozygous mean?
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-two alleles of the same gene are identical
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What is a phototroph?
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-does not require nutritional supplement to grow
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What does auxotroph mean?
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-requires nutritional supplement to grow through mutation
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What are the different levels of effects of mutations?
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-undetectable
-slight -severe -lethal |
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What determines the effect of mutations?
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-depends on what gene product (protein) is affected
-to what extent it's function is affected |
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What are 7 different mutations?
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-spontaneous
-mutagen (chemical)-induced -point -insertion -deletion -substitution (missense and nonsense) -frame-shift |
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What are spontaneous mutations?
Point? Insertion? Deletion? |
-natural radiation; replication
-change in one base pair -insertion of one or more base pairs -removal of one or more base pairs |
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What occurs in Substitution mutations?
Missense? Nonsense? Frame-shift? |
-replaces one or more base pairs
-changes one amino acids -introduces stop codon -changes reading frame of protein |
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What are 3 types of mutants?
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-non conditional
-conditional -reverant |
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How do non-conditional mutants express?
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-expresses mutant phenotype under all conditions
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How do conditional mutants express?
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-expresses phenotype under restrictive conditions but not permissive conditions
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How do revertant mutants express?
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-mutant that regained wild-type phenotype
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What are the different types of conditional mutants?
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-temperature-sensitive (ts):
+heat-sensitive and cold sensitive |
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What do mutagens help with?
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-increase probability of finding mutants: 10^-4 or higher vs. spontaneous (10^-8 to 10^-9)
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What are mutant selections?
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-positive selection
-mutant cells preferentially grow versus non-mutatnt cells such as antibiotic-resistant mutants |
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What are mutant screens?
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-negative selection
-mutant cells do not preferentially grow versus non-mutant cells such as replica plating to identify mutants |
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What are three mutagen-induced mutagenesis?
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-chemical mutagens
-radiation-ionizing and non-ionizing -error-prone DNA repair |
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What are the three types of chemical mutagens?
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-base analogs
-alkylating agents -intercalating agents |
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What are base analog chemical mutagens?
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-resemble purine and pyrimidine bases; defects during replication
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What are alkylating agent chemical mutagens?
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-directly alter bases such as ethyl methane sulfonate (EMS), nitrosoguanidine, mustard gas
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What are intercalating agent chemical mutagens?
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-insert between base pairs causing insertions/deletions during replication such as ethidium bromide, acridines
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What are non-ionizing radiation mutagens?
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-UV light
-DNA and RNA absorb UV light -creases thymine dimers; covalent cross-link between adjacent T bases -disrupts replication |
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What do ionizing radiation mutagens cause?
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-causes water and other molecules to ionize
-creating mutagens such as hydroxyl radical (OH-) |
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What occurs in error-prone DNA repair?
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-most DNA repair is error-free with templates
-without template, information leads to mutations *SOS system uses an error-prone DNA polymerase |
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What does the SOS system use?
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an error-prone DNA polymerase
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What are some uses of genetic analysis?
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-functions of proteins
-metabolic pathways and regulatory networks -correlate an in vitro biochemical function to an in vivo function -determine site of action of external agents (Ab's) -define relationships between seemingly unrelated systems or proteins -indentify interactions between two or more proteins -screen for cancer-causing substances in environment (Ames test); mutagens are also oncogenic (cancer-causing) |
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What is the Ames test and what year was is created?
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-screen for cancer-causing substances in environment
-1975 -85%, $600, 2 days VS 100%, $100,000, 3 years |
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How do you perform an Ames Test?
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-use a control and experiment with liver extract
-in experiment tube, add suspected mutagen (such as shampoo) -cuture his- salmonella and put on plate lacking histidine -incubate and see if growth occurs *growth means mutation occurred and allowed for reversion of his- to his+ |
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What is transformation?
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-free DNA in environment and a competant recipient
-donor is dead and recipient is living |
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What is transduction?
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-bacteriophage is required, donor is killed by it and recipient is living
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What is conjugation?
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-cell to cell contact and F plasmid has a living donor and living recipient
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What are three natural mechanisms of horizontal genetic transfer in bacteria?
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-transformation
-transduction -conjugation |
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What encodes antibiotic resistance factors?
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-plasmids and bacteriophages
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What encodes virulence factors?
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-mobile bacteriophage
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What encodes exotoxins?
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-bacteriophage
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What is ETEC?
EHEC? |
-enterotoxigenic E. coli exotoxins LT and ST
-enterohemorrhagic E. coli exotoxin Shiga-like Toxin (SLT) |
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What is the cornerstone of modern molecular biology?
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-transformation
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What is competency?
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-ability of cell to uptake DNA; several proteins are required for uptake
-not all cells are competent to be transformed |
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In terms of competency, what can cells be?
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-naturally competent (constitutive)
-induced naturally competent -induced competency (divalent cations, protoplasts, electroporation |
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Can all phages mediate transduction?
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-no, only certain ones
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What plays an important role in bacterial evolution?
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-transduction
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What are two types of transduction?
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-generalized transuction
-specialized transduction |
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What is generalized transduction?
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-any piece of chromosomal DNA can be incorporated into phage and transduced to other cell
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What is specialized transduction?
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-only chromosomal DNA adjacent to integration site of bacteriophage can be incorporated into phage
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Who discovered conjugation?
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-Lederberg in 1946
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Where are genes regulating conjugation found?
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-on conjugative plasmids
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What is an F+ strain?
F- Strain? Hfr strain? F' Plasmid |
-contains F plasmid
-no F plasmid -F plasmid integrated into the chromosome recombination occurs at multiple insertion sequences (IS) -F plasmid that contains chromosomal DNA |
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What does complementation require and what is it used for?
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-requires two copies of gene be present in same cell (does not require recombination to occur)
-used to determine number of genes responsible for phenotype -used to classify different mutant alleles |
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What are partial diploids?
How are they formed? |
-merodiploids
-use plasmids or phage containing pieces of DNA |
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How can you tell if two mutations are on the same gene or not?
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-if they complement, they are in different genes
-noncomplementation means they are in same gene |