Ch.8 Flashcards
What determines the phenotype of a cell?
Change in genotype often changes observable characteristics called phenotypes
- influenced by environmental conditions
What is the source of variation among microorganisms that were once identical? (What gives organisms their variation if they were once identical?)
Mutation
What is the definition of transposons?
- jumping genes
- pieces of DNA that can move from one location to another in a cell’s genome; process of transposition
- provide mechanism for moving DNA
Which are the chemical mutagens that mimic naturally occurring bases?
Base analog: Resemble nucleobases, but have different hydrogen-bonding properties
- incorporated into DNA by DNA polymerase
What causes thymine dimers?
Ultraviolet light causes thymine dimers
What removes thymine dimers?
- Photoreactivation: light repair
– Enzyme uses energy from light
– Breaks covalent bonds of thymine dimer
How do X-rays cause mutations?
Radiation
- X rays cause single- and double-strand breaks in DNA
Which Domains of organisms possess DNA repair mechanisms?
Bacteria, Archaea, and Eukarya
How does mismatch repair fix mutations in DNA?
- Repair fixes errors missed by DNA polymerase
- Enzyme cuts sugar-phosphate backbone of new DNA strand
- Another enzyme degrades short region of DNA strand with error
- DNA polymerase fills in correct nucleotide and DNA ligase seal the gap
Eukaryotes may mask the effects of mutations while prokaryotes do not. How come?
Their diploid nature, meaning they have two copies of each gene, allowing a functional copy to compensate for a mutated one
What is direct selection?
- used to isolate mutants
- Cells inoculated onto medium that supports growth of mutant but not parent
- Antibiotic-resistant mutants grow on medium with the antibiotic, but parents do not
What is replica plating used for?
indirectly selects auxotrophs from prototrophic parent strain
Which technique is used to increase the proportion of auxotrophic mutations in a population of bacteria?
Penicillin Enrichment
Which test is used to identify potential carcinogenic mutagens?
Ames test identify potential carcinogenic mutagens
What is transduction?
- bacterial DNA transfer by bacteriophages (phages)
- Phages infect bacterial cells
1. Attaches and injects its nucleic acid into cell
2. Phage enzymes cut bacterial DNA into small pieces
3. Bacterial cell enzymes produce phage nucleic acid and a phage coat
4. Phage particles are released from bacterial cell
