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58 Cards in this Set

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