The purpose of the step at 72°C is A. binding of DNA polymerase to the DNA B. binding of the primers to single stranded DNA C. denaturation of DNA D. Synthesis of a complementary stra

The purpose of the annealing step is A. Synthesis of a complementary strand B. binding of the primers to single stranded DNA C. denaturation of DNA D. binding of DNA polymerase to the DNA

You are programming a thermocycler and are setting temperature of the second step in your protocol to 62°C. What is happening during this step?ANSWERIt separates double-stranded DNA into single strands that can be copied.It allows the primers to anneal.Nothing is happening at this temperature, as DNA replication is halted.The temperature allows DNA polymerase to copy the target DNA.

The DNA strands are separated by _____________ for DNA polymerase to bind A. Helicase B. Gyrase C. Heat denaturation D. Annealing

Which is true during DNA replication?Group of answer choicesDNA ligase is the last step of the polymerisation reaction for the lagging strand, but is not used on the leading strand.DnaA binds to regions that are rich in AT as this purine-purine base pairing forms only two hydrogen bonds.The β sliding clamp prevents the dissociation of DNA polymerase III, increasing the length of DNA each polymerase can synthesise.DNA gyrase binds to and applies tension to the lagging strand.

DNA polymerization is one of the most conserved mechanisms of genome replication.  Synthesis of a complete DNA strand requires a template, primers, a polymerase enzyme, and sufficient deoxyribonucleotide triphosphates (dNTPs).  The DNA polymerase enzyme binds consecutive base pairs on the template strand and extends the double helix by adding dNTPs to the primer.  The amino acid residues in the active site of DNA polymerase form hydrogen bonds with Watson-Crick donors and acceptors on incoming DNA nucleotides to facilitate base pairing.The formation of the DNA double helix creates opposing changes in entropy and enthalpy.  Favorable bonding interactions via hydrogen bonds during Watson-Crick base pairing results in negative enthalpy, and restricted rotation and flexibility of the DNA backbone generates negative entropy.  Scientists hypothesize that hydrogen bonding between bases not only stabilizes the double helix but is also crucial for selective and efficient replication.Analogs that are similar in size and shape to naturally occurring bases can be used to determine the influence of hydrogen bonding on base pair selectivity.  To mimic the structure of deoxythymidine triphosphate (dTTP), researchers synthesized dNTP derivatives of difluorotoluene (dFTP).  dFTP is a nonpolar analog of dTTP that lacks Watson-Crick hydrogen bonding.  Klenow fragment polymerase (KF), which has 3′-5′ but not 5′-3′ exonuclease activity, was incubated with a mixture of DNA template, primers, and dNTPs, including dFTP.  The efficiency of dFTP and natural dTTP nucleotide incorporation into a growing primer strand by KF is shown in Figure 1.Figure 1  Template-specific selection of dFTP and dTTP by the KF enzymeAdapted from Moran S, Ren RX, Kool ET. A thymidine triphosphate shape analog lacking Watson-Crick pairing ability is replicated with high sequence selectivity. Proc Natl Acad Sci USA. 1997;94(20):10506-11. Question 44The Klenow fragment used in the experiment would be able to perform which of the following repair processes?A.Correction of mismatched nucleotides in the middle of a completed strandB.Replacement of nucleotides at the 3′ end of the growing strandC.Excision of thymine dimers at the 5′ end of the growing strandD.Removal of damaged bases from the middle of the template strand