Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
DNA Replication
Biochemistry Ch. 28
| Question | Answer |
|---|---|
| What is "the end problem" of Eukaryotic DNA-Replication? | The DNA Polymerase that removes the RNA-primer, at the end of replication, removes it from the 5'-end of the lagging strand, and continues to the 3'-end of its Okazaki fragment. So the newly produced strand is a sequence-length shorter than its template. |
| How do Eukaryotic chromosomes differ from Prokaryotic? | Eukaryotic chromosomes are linear. Prokaryotic chromosomes are closed circles. |
| What are Telomeres? | Telomeres are unique structures located at the ends of linear chromosomes. |
| What are Telomeric sequences? | Telomeric sequences are thousands of copies of repeats of short sequences. |
| What is responsible for making Telomeres? | The enzyme that builds telomeres is called telomerase. |
| How do Telomeres answer "the end problem"? | With each round of DNA replication, linear chromosomes in eukaryotes shorten. Thus, the more telomeric sequences a chromosome has, the more divisions it can undergo before the telomeres are "eaten up". |
| What is unique to the enzyme Telomerase? | Telomerase is a reverse transcriptase - an enzyme that uses an RNA template (a circular RNA that it carries) to synthesize DNA. That is how it replicates at the END of a DNA. |
| Is DNA damage the same thing as DNA mutation? | DNA damage is DIFFERENT from DNA mutation. |
| Where does the RNA template that Telomerase carries on itself bind to the DNA? | The RNA template pairs with the 3'-end of the linear DNA. |
| In what ways can bases be damaged? | Bases can be damaged by Oxidizing Agents, Alkylating Agents, and UV light. |
| What are Mutagens? | Chemical agents that can alter specific bases within DNA AFTER replication is complete. |
| Hydroxyl Radicals are an example of what? | Hydroxyl Radicals are a type of Mutagen. |
| How do Hydroxyl Radicals damage DNA? | Hydroxyl Radicals alter the edge of DNA it base-pairs with, changing its base-partner to Adenine, and not the normal Cytosine. |
| What is Deamination? | Deamination is a type of DNA damage. It removes the Amine of the base, which essentially changes its base pairing. |
| What is Alkylation? | Alkylation is a type of DNA damage. Electrophile are attacked by nucleophiles, to form Alkylated Adducts. This results in hightened electrophile activity of the base, and GC to TA traversion. |
| What is an example of Base Alkylation by an Alkylation Agent? | Aflotoxin, created by peanut mold, is converted by Cytochrome enzyme to become a highly reactive epoxide that reacts with G to form a mutagenic adduct, causing GC-TA traversion. |
| How do UV rays damage DNA bases? | UV rays induce cross-links of residues within DNA strands, resulting in Thymine and Pyrimidine Dimers, that halt DNA replication. |
| What do UV rays do to Pyrimidines Residues? | UV rays covalently link adjacent Pyrimidine residues along DNA strands. This disables the body's ability to replicate DNA until the Pyrimidine Dimer is removed from the DNA double helix. |
| What do UV rays do to Thymine Residues? | UV rays induce intrastrand (within the same DNA strand) cross-linking. Results in Thymine Dimers. |
| Are all Intrastrand cross-links caused by UV rays? | No. Intrastrand cross-link can be caused by compounds, like Psoralens, whose two active sites form adducts with nucleotide bases. Thus disrupting replication by preventing strand separation. |
| How do X-rays cause DNA damage? | X-rays are Mutagenic. They induce single and double-stranded breaks in DNA. Drosophilia is an example. |
| What are the parts of Single-Strand DNA Repair System Mechanism? | 1- Recognize the offending Base(s) 2- Remove the offending Base(s) 3- Repair the resulting gap with a DNA Polymerase and DNA Ligase |
| What are important Repair Mechanisms in essentially all cells, that's NOT proof-reading activity? | Base Excision, Nucleotide Excision, and Mismatch Repair. |
| What is Mismatch Repair System? | A Non-proofreading repair mechanism that requires 2 or more proteins (1 for detecting the mismatch, 1 for recruiting an endonuclease to cleave the newly synthesized DNAstrand near the lesion). Example is E-Coli's Mismatch Repair System. MutS, MutL, MutH. |
| What is Base Excision Repair? | Excision of modified bases, such as 3-methyladenine by the E.Coli enzyme AlkA. Uridine bases in DNA, formed by deamination of Cytosine, are excised & replaced. |
| What is Nucleotide-Excision Repair? | Repair of a region of DNA containing a Thymine Dimer, by the sequential action of uvrABC exinuclease, DNA Pol I, and DNA Ligase. |
| What can DNA Ligase do? | DNA Ligase can seal simple breaks in only ONE strand of the DNA backbone. DNA Ligase catalyzes the joining of one DNA strand having a free 3'-OH to another DNA strand that has a free 5'-phosphate group. It works only on single-strand DNA. It requires ATP. |
| How can mutation be quantified? | The Ames Test. Addition of a chemical mutagen to the center of the petri dish results in new mutations. A series of concentrations of chemicals can be readily tested to generate a dose-responsive curve. |
| Recombination is important in the metabolism of what? | Recombination is important in DNA metabolism. |
| How does recombination affect DNA replication? | When DNA replication stalls, recombination process can reset the replication machinery so that replication continues. |
| How can recombination affect breaks in double-strand DNA? | Some double-stranded breaks in DNA are repaired by recombination. |
| What is Huntington's Disease? | Disease caused by a replication phenomena wherein tandem/triplet-repeat-sequences get copied INcorrectly. The template strand undergoes slip-age backwards, causing a loop of template-sequence that goes unpaired, and an expanded array of triplet repeats. |
| Error-related systems associated with cancer include what? | Error-related systems associated with cancer include HNPCC (colon cancer) and BRC-A which is involved in DNA repair. |
| What is p53? | p53 is an important proto-oncogene that ensures DNA fidelity is p53 by stopping the cell cycle if DNA replication has not completed properly. Then, acting as a transcription factor, it activates transcription/translation of DNA repair genes. |
| Why is the Ames Test used? | The Ames test is used to test the tendency of a compound to cause mutation. |
| What information from the Ames Test quantifies mutation? | It works by using a plasmid with a single base mismatch in a gene marker that stops expression to give the marker (blue color, for example). Comparing the rates of marker production, the tendency of a compound to cause mutation can be determined. |
| In what part of the Cell Cycle is Recombination most active? | The process can be quite active during meiosis. |
| Recombination proceeds through formation of what? | Holliday junctions form as a result of homologous sequences alignment, strand cleavage on each chromosome, invasion of the strands into the opposite chromosome, movement of the junction, another cleavage reaction, then reformation of phosphodiester bonds. |
Created by:
abenvie
Popular Biology sets