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BIO-215 Chapter 8
| Question | Answer |
|---|---|
| Who discovered jumping genes | Barbara Mclintock; observed different colored corn kernals |
| Staphylococcus aureus | Gram-positive, causes skin and wound infections, has become resistant to antibiotics |
| Transposase | Facilitates recombination between inverted repeats; transposon is cut from its original location and moved |
| What are two mechanisms of genetic change in bacteria? | Mutation and Horizontal gene transfer |
| Prototroph | Does not require growth factors |
| Auxotroph | Requires growth factors |
| True or False: Environment causes mutations | False |
| Point mutation | Change of a single base pair |
| Silent mutation | wild-type amino acid |
| Missense mutation | different amino acid; may only be partially functional, called leaky |
| Nonsense mutation | Stop codon, shorter protein |
| What is a mutation that inactivates a gene called? | A null or knockout mutation |
| What happes when ROS oxidize guanine? | DNA polymerase often mispairs with adenine |
| What are the results of deletion of insertion? | Frameshift, shortened nonfunctional, or knockout mutation |
| Transposon | Can move from one location to another, function of gene is destoyed, most have transciptional terminators |
| Transcriptional Terminators | Block expression of downstream genes in operon |
| What causes an induced mutation? | Mutagen |
| Chemical mutagens | May cause base substitutions or framshift mutations |
| Nitrous Acid | Converts Cytosine to uracil, pairs with adenine instead of guanine |
| Alkylating agents | Add alkyl groups onto nucleobases |
| Nitroguanidine | Adds methyl group to guanine, pairs with thymine |
| Base analogs | Resemble nucleobases but have different hydrogen-bonding properties and can be mistakingly incorporated by DNA polymerase |
| 5-bromouracil | Resembles thymine but pairs with cytosine |
| 2-amino purine | Resembles adenine but pairs with cytosine |
| Intercalating agents | Cause frameshift mutations; are flat molecules that insert between adjacent base pairs |
| Transposition | Used to generate mutation, inserts into cell’s genome, inactivates gene |
| Ultraviolet irradiation | Forms, thymine dimers that causes covalent bonds between adjacent thymines that can’t fit into the double helix; also causes replication and transcription stall at distortion |
| X rays | Cause single ad double strand breaks in DNA, double breaks often produces lethal deletions |
| Defect: Copying errors during replication | Repair: Mismatch repair |
| Defect: Spontaneous chemical or radiation damage to a single base | Repair: Base excision repair |
| Defect: Chemical or radiation to a segment | Repair: Nucleotide excision repair |
| Defect: Ionising radiation, chemotheray, and free radicals | Repair: Double stranded break repair |
| Mismatch repair | 1. Enzyme cuts sugar-phosphate backbone 2. Another enzyme degrades short region of DNA strand 3. Methylation of DNA indicates template strand 4. DNA polymerase and ligase make repairs |
| Base Excision Repair | 1. Glycosylase removes oxidized nucleobase 2. Another enzyme cuts DNA at this site 3. DNA polymerase removes short section; synthesizes replacement 4. Ligase seals gap |
| Photoreactivation | 1. Enzyme uses energy from light 2. Breaks covalent bonds of thymine dimer 3. Only in bacteria |
| Excision repair | 1. Enzyme remove damage 2. DNA polymerase and DA ligase fix |
| SOS repair | Genes in SOS activated, DNA polymerase that synthesizes at extensive damage, no proofreading, result is SOS mutagenesis |
| Direct Selection | Cells inoculated onto medium that supports growth of mutant but not parent |
| Indirect selection | Isolates auxotroph from prototrophic parent strain |
| Ames test | measures effect of chemical on reversion rate of histidine-requiring Salmonella auzotroph |
| Who discovered transformation? | Frederick Griffith in 1928 |
| Describe how transformation happens. | 1. dsDNA encoding streptomycin resistance binds to receptor on surface of the competent cell 2. One strand enters the cell; nuclease degrades other 3. New DNA integrated via homologous recombination 3. One daughter will inherit donor DNA |
| What are the steps of transduction? | 1. Phages infect and hijack 2. Phage goes to different cell, where DNA is incorporated |
| What are the steps of conjugation? | 1. F plasmid transferred 2. Hfr cell with incorporated F Plasmid makes F pilus and DNA is transferred, usually incomplete |
| Transposons: Insertion sequences | Transposase gene flanked by short repeat sequences; move to different location in DNA in same cell |
| Transposons: Composite transposons | Recognizable gene flanked by insertion sequences; same as insertion sequences, but encode additional information |
| Genomic Islands | Large fragment of DNA in a chromosome or plasmid; Code for Gees that allow cell to occupy specific environmental locations |
| Phage DNA | Phage Genome; may encode proteins important to bacteria |
| Plasmids | Circular dsDNA replicon; smaller than chromosomes; generally code only for non-essential genetic information |
| What does CRISPR stand for? | Clusters of regularly interspersed short palindromic repeats |
Created by:
Isabelli
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