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Bis 101
Lecture 12 Final
| Question | Answer |
|---|---|
| What is a mutation? | A heritable change in the genetic material. It is necessary for the evolution and continuation of life. |
| What is a point mutation? | A mutation that affects only a single base pair |
| What are the two basic mutations? | Base substitutions and base indels |
| What is a base substitution? | When a nucleotide is replaced with another nucleotide, usually goes from purine to pyrimidine or vise verse |
| What is a base indel? | Stands for insertion or deletion, when a base is randomly inserted into or deleted out of the code |
| What is a silent mutation? | When a mutation does not code for a different amino acid because the amino acids are degenerate. Can also be called a synonymous mutation. |
| What is a missense mutation? | When a change in the sequence codes for one different amino acid than normal. It is a conservative mutation if it codes for a chemically similar amino acid. Nonconservitive if chemically dissimilar. |
| What is a nonsense mutation? | When a normal codon is changed into a stop codon. This results in a truncated polypeptide |
| What is a frameshift mutation? | Addition or subtraction of nucleotides that are not in groups of three |
| How is splicing affected by point mutations? | It can alter where the splicing zone is so that either intron code gets coded in the final mRNA or that some of the exon code gets spliced out |
| Which mutations are the result of base substitution? | Missense, nonsense, silent |
| Which mutations are the result of indel mutations? | Frameshift mutation |
| Where can a mutation occur outside of the transcription zone? | In the promoter and in the regulatory systems or operator site. This affects the rate of production of a certain protein. |
| What is a genetic mosaic? | A phenotype resulting from patches of genetically altered tissue |
| What is the difference between somatic and germ-line mutations? | A somatic mutation will affect portions of the organism in patches while a germ-line mutation will affect the entire organism. Also a germ-line mutation will carry on the mutation to its offspring, a somatic mutation will not. |
| What is a spontaneous mutation? | Mutations that result from abnormalities in biological processes |
| What is an induced mutation? | Mutations brought on by environmental agents. This is brought on by chemicals often times and has a higher mutagenic rate than spontaneous mutations. |
| What is the mechanism for spontaneous mutations? | 1: Transposition insertion (don't need to know the details) 2: Indels caused by slippage during DNA replication 3: Replication errors causing base substitution or 4: chemical changes in base |
| What kind of mutation does replication slippage cause? | Indel mutations |
| What are base replacements? | When rare base tautomers mispair with one another. |
| What is deanimation? | When the bases are molecularly changed and now look like a different molecule. (Most often Cytosine becomes Uracil) |
| What did Luria and Delbruck demonstrate? | Spontaneous mutation occur normally and not as a result of environmental stimuli |
| How do chemical mutagens alter DNA? | They disrupt pairing by 1: Using base analogues 2: Alkylating bases or 3: Modifying nucleotide structures |
| How do base analogues affect DNA? | They have more frequent mispairings |
| How do Alkylating bases agents affect DNA? | They induce base damage which then induces mispairing |
| What is an intercalating agent? | A chemical mutagen that inserts between the bases and distorts the helix. Charring your food can do this. This induces indel mutations. |
| What does the Ames test reveal? | Mutagenic compounds by mixing them with organic matter then plating them. |
| What kind of physical mutagens alter DNA? | Ionizing radiation can induce intra-strand cross-linking between pyrimidines. This binds the strand to itself and disconnects it from its adjacent bases. |
| How does direct reversal DNA repair work? | The UV damaged cells must be exposed to visible light. The photolyase found in bacteria and yeast uses the light as energy and corrects the mutation. Does not work in eukaryotes. |
| How does base excision repair alter DNA? | It removes Uracil from DNA and repairs for Alkylation and deanimiation of the bases. DNA glycolase removes the damaged base it making an AP site. AP endonuclease cleaves the DNA. Bases are then excised and re-synthesized. |
| How does nucleotide exision repair alter DNA? | Most common DNA repair system. Works for a few bases being damaged. The intact undamaged strand is used as a template to re-syntehsize. |
| Explain the process for Nucleotide exision repair. | UvrA-UvrB tracks the DNA looking for damages. When a damage is found UvrA is released and UvrC binds to UvrB. UvrC cuts on both sides of the thymine dimer. UvrD removes the cut damaged region. DNA polymerase fills in the gap and DNA ligase connects. |
| How does mismatch repair alter the DNA? | This happens after DNA replication. It corrects errors made by DNA polymerase |
| What is tranlesional DNA synthesis? | If the bases cannot pair then replication will stop. Translesion DNA polymerase can skip over damanges sequences so replication can be completed. Some proteins insert the correct bases, some fill in with random bases. |
| In DNA repair what does it mean when non-homologous ends are joining? | When there is a break in both strands, the DNA is trimmed to create flush DSB ends. Special DNA ligase rebonds both ends. Some bases are lost and this results in mutation. |
| In DNA repair what is a homologous rejoining? | When there is a double break in the DNA strand, the DNA invades the strand of a homologous chromosome and uses it as a template to fix itself. |
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24rory
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