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18 Cards in this Set
- Front
- Back
A gene is a segment of genetic material that specifies a functional unit in the form of what
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A polypeptide chain; an RNA molecule; a binding site for enzymes or proteins that regulate gene expression
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Compare genotype and phenotype
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Genotypic variation is a rare event, and the altered properties in the variants (mutants) are stable, heritable and not readily reversible. Phenotypic variation is a physiological adaptation of the whole population of the culture to a change in the culture condition. Phenotypic variation is readily reversible
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Are bacteria diploid or haploid
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Haploid. Bacterial chromosomes can be circular or linear. Some bacteria have two chromosomes
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What are the major functions of a bacterial chromosome
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Replication (from Origin of Replication to the terminus); Gene expression
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What does gene expression consist of
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Transcription and translation
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How are bacterial mutations defined
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Heritable changes in the genome that result in genotypic variation
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What are the 4 types of mutations
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Base substitutions; Insertion; Deletion; Rearrangements
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What are the main mutation phenotypes
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Silent; Loss of function (Missense, Nonsense or Frameshift); New function (evolution)
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What are some common mutant phenotypes
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Auxotrophic (new nutritional requirement due to loss of ability to synthesize a compound); Resistant; Altered morphology; Fermentation; Conditionally lethal
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How do mutations arise
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Spontaneously and randomly within a population in the absence of any agent that might select for the mutant variant
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How can mutation frequency be increased
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By mutagens, including those that are physical, chemical, or biologic
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What are mutator genes
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Low mutation frequency in bacteria is due to DNA repair enzymes. Genes encoding the repair enzymes are called mutator genes since mutations in these genes affect the frequency of mutations in other genes
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What is reversion
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Restores the DNA sequence to the same as in the wild type
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In bacterial genetics, what is suppression
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The original mutation remains, but the phenotype of the mutant has been corrected or suppressed by a second mutation. Includes Intragenic and Extragenic suppression
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What are two specific DNA repair pathways in bacteria
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Repair of deaminated bases; photoreactivation
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What are some general DNA repair mechanisms in bacteria
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Excision repair; Methyl-directed mismatch repair; SOS inducible repair
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What is xeroderma pigmentosum
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Fibroblasts are deficient in excision of thymidine dimers; explains hypersensitivity to sunlight
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What is Hereditary nonpolyposis colon cancer
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Results from mutations in hMSH2, and methyl-directed mismatch repair enzyme
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