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Which of the following joins Okazaki fragments during prokaryotic DNA replication?
Which strand of DNA is replicated exclusively in a discontinuous fashion?
Which of the following is not a function of DNA Polymerase III?
b. Ligating the final products
d. Clamping on to the template
e. None of these are functions of DNA Polymerase III
Which of the following mechanisms can serve to repair double-stranded breaks in DNA?
recombination & non-homologous end joining
What is the nucleophile in the DNA polymerase mechanism?
the 3' hydroxyl on the deoxyribose
Is the following statement true or false?
"The flow of genetic information in the cell is always DNA → RNA → protein."
Retroviruses carry their genetic information in the form of RNA, which is reverse-transcribed to DNA. This DNA then follows the path DNA → RNA → protein using the synthetic apparatus of the virus-infected cell.
-Two replication forks form at each origin of replication.
-At the forks, the two strands of double-stranded DNA are separated, and DNA polymerase acts to synthesize a new strand of DNA on each of the separated strands.
Why is it necessary to unwind the DNA helix in the replication process?
The separation of the two strands of DNA requires an unwinding of the helix.
DNA-polymerase enzymes also function as exonucleases.
Most DNA polymerases are also exonucleases.
Suggest a reason for the rather large energy excess available in the insertion of a deoxyribonucleotide into a growing DNA molecule. (About three times as much energy as is necessary is available in the reaction dNTP + DNAn → DNAn+1 + pyrophosphate.)
The very favorable forward reaction means that the reverse reaction is very unfavorable.
This strong forward reaction driving energy effectively inhibits the depolymerization reaction DNAn + pyrophosphate → dNTP + DNAn-1.
Makes RNA primers.
makes a short section of RNA to act as a primer for DNA synthesis.
Single-strand binding protein
Protects single-stranded DNA from nucleases.
DNA polymerase enzyme
Provides the sequence for the newly synthesized DNA.
links together small, newly formed strands of DNA to make longer DNA segments.
introduces a swivel point in advance of the replication fork.
What is the primer in DNA replication?
short segment of RNA to which the growing DNA chain is bonded.
The primer is a short stretch of RNA hydrogen-bonded to the template DNA to which the growing DNA strand is bonded at the start of synthesis.
How does proofreading take place in the process of DNA replication?
DNA polymerase uses its exonuclease activity to remove a mismatched nucleotide.
Proofreading is a process of removal of a newly added incorrect nucleotide. The DNA polymerase enzyme uses its 3'-exonuclease activity to remove the incorrect nucleotide and then uses its polymerase activity to attach the correct nucleotide before proceeding with the DNA chain extension.
why can methylation of nucleotides play a role in DNA replication?
DNA in prokaryotes is methylated on select residues. Repair enzymes can detect the difference between the parental strand and the newly synthesized strand by this methylation.
Prokaryote DNA is methylated at select sites. This methylation occurs subsequent to DNA synthesis. Thus, for a short time after synthesis, the parental DNA template strand is methylated while the newly synthesized strand is not. Repair enzymes that recognize a base pair mismatch between the strands will remove and replace the mismatched base on the unmethylated strand.
How do the DNA polymerases of eukaryotes differ from those of prokaryotes?
-Prokaryote DNA polymerases produce longer Okazaki fragments than eukaryote DNA polymerases.
-Eukaryotes tend to have a greater diversity of DNA polymerases.
-Eukaryote DNA polymerases tend to be larger than prokaryote DNA polymerases.
-Eukaryote DNA polymerases usually do not have exonuclease activity, in contrast to DNA polymerases from prokaryotes.
Telomerase is a ribonuclear protein containing a section of RNA complementary to the telomere.
If telomerase was inactivated DNA synthesis would stop.
If telomerase was inactivated the chromosome would shorten.
Without telomerase, the chromosome would eventually shorten, and the cell would no longer be able to replicate its DNA correctly.
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