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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
A polypeptide chain; an RNA molecule; a binding site for enzymes or proteins that regulate gene expression
Compare genotype and phenotype
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
Are bacteria diploid or haploid
Haploid. Bacterial chromosomes can be circular or linear. Some bacteria have two chromosomes
What are the major functions of a bacterial chromosome
Replication (from Origin of Replication to the terminus); Gene expression
What does gene expression consist of
Transcription and translation
How are bacterial mutations defined
Heritable changes in the genome that result in genotypic variation
What are the 4 types of mutations
Base substitutions; Insertion; Deletion; Rearrangements
What are the main mutation phenotypes
Silent; Loss of function (Missense, Nonsense or Frameshift); New function (evolution)
What are some common mutant phenotypes
Auxotrophic (new nutritional requirement due to loss of ability to synthesize a compound); Resistant; Altered morphology; Fermentation; Conditionally lethal
How do mutations arise
Spontaneously and randomly within a population in the absence of any agent that might select for the mutant variant
How can mutation frequency be increased
By mutagens, including those that are physical, chemical, or biologic
What are mutator genes
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
What is reversion
Restores the DNA sequence to the same as in the wild type
In bacterial genetics, what is suppression
The original mutation remains, but the phenotype of the mutant has been corrected or suppressed by a second mutation. Includes Intragenic and Extragenic suppression
What are two specific DNA repair pathways in bacteria
Repair of deaminated bases; photoreactivation
What are some general DNA repair mechanisms in bacteria
Excision repair; Methyl-directed mismatch repair; SOS inducible repair
What is xeroderma pigmentosum
Fibroblasts are deficient in excision of thymidine dimers; explains hypersensitivity to sunlight
What is Hereditary nonpolyposis colon cancer
Results from mutations in hMSH2, and methyl-directed mismatch repair enzyme