| Question |
Answer |
| DNA replication is _______ and ________ |
bidirectinal and semiconservative |
| What is one important difference between eukaryotic and prokaryotic DNA replication? |
Prokaryotic DNA replication has one origin |
| Origin of replication sequences are usually almost exclusively made up of what base pairs? |
A and T |
| What is the job of single-stranded DNA-binding protein? |
It binds to to the single strands in the separated regions to prevent them crom reannelaing so replication enzymes can function. Also protects the strands from nuclease degredation |
| DNA helicases do what job? |
Unwind the helix (like a zipper) |
| Type I topoisomerase cuts _____ strand(s) and allowing the DNA to _________. After it is complete it seals the nicked strand. |
1, swivel to relieve the supercoil. |
| Type II topoismerase cuts _______ strand(s) |
2 |
| All polymerases that synthesize nucleic acids can only catalyze synthesis in this direction ____. Therefore the template is read in this direction ____. |
5' to 3', 3' to 5' |
| DNA prokaryotic polymerases require a ____ group to begin synthesis. This requirement is met by a _______, which is synthesized by this enzyme _______ and does not require a primer |
RNA primer, RNA polymerase |
| Each nucleotide requires the energy of hydrolysis of ____ high energy bonds |
2. pyrophosphate is released from the dNTP, which is then further hydrolized to pyrophosphatase. |
| Is the enzyme responsible for catalyzing chain elongation in prokaryotes for both the leading and lagging strands. |
DNA Polymerase III |
| Prokaryote Pol III has _________ activity which allows it to replicate DNA with as much fidelity as possible. It checks each newly added nucleotide for accuracy. |
proofreading |
| Prokaryote Pol III exonuclease works in this direction |
3' to 5' |
| DNA polymerase I catalyzes what reaction? What direction does it function? |
removal of RNA primer and replacment with dNTPs. 5' to 3' exonuclease which removes the RNA primer. It also contains 3' to 5' exonuclease (proofreading) ability |
| What does DNA ligase do? |
seals the gap that remains after Pol I removes the RNA primer and replaces it with DNA |
| During what cell cycle phase do eukaryotic cells replicate their DNA? |
S phase |
| Name the two important eukaryotic DNA polymerases |
Pol alpha, Pol delta |
| What produces the RNA primer in Eukaryotic DNA replication? |
Pol alpha (it also contains DNA polymerase activity) |
| This enzyme extends the leading and lagging DNA fragments in Eukaryotic DNA replication that began by Pol alpha. It also contains DNA proofreading activity |
Pol delta |
| Describe the unique problem created in Eukaryotic DNA replication to complete the replication. What enzyme solves this problem? |
Eukaryotes contain linear DNA, therefore at the end of the lagging strand there will be a gap where the final RNA primer was removed. The enzyme is telomerase |
| The ends of eukaryotic DNA contain repeated sequences called ______ |
telemoeres |
| Telomerase is only present in what kind of cells? |
Cells that continually divide and are not terminally differentiated. |
| Telomerase is a certain type of this kind of enzyme |
reverse transcriptase |
| Some polymerases can copy an RNA template into DNA in the process known as ________ |
reverse transcription. |
| Reverse transcriptase lacks ______ ability. |
proofreading |
| A defect in the mismatch repair system has been shown to cause this disease |
hereditary nonpolyposis colorectal cancer (HNPCC), one of the most common inhereted cancers |
| This type of enzyme recognize a misincorporated nucleotide, nicks the strand, and remove sthe misincorporated nucleotide. |
endonucleases |
| The rare genetic disease zeroderma pigmentosum most often originates from a deficiency in this enzyme |
excision endonuclease |
Ch.18 LTI-MA 509
