The cytosolic production of deoxyribonucleotides prior to DNA replication requires the reduction of ribonucleoside diphosphates in a multistep mechanism that involves free radicals and the ultimate use of NADPH as a reducing agent.  The cellular store of this reducing agent is produced primarily from:A.the citric acid cycle.B.glycolysis.C.fatty acid metabolism.D.the pentose phosphate pathway.

The pentose phosphate pathway Group of answer choicescreates NADP+ for processes like reductive biosynthesiscreates NADH, which will carry electrons to the respiratory chain to facilitate ATP productioncreates a 5 carbon sugar that is a precursor for key molecules like nucleic acidsis not regulated by soluble coenzymes in the cell

A. Increased activity of the pentose phosphate pathway B. Increased production of NADPH C. Decreased activity of the pentose phosphate pathway D. Increased production of NADP

Which of the following enzymes is responsible for unwinding the DNA double helix during replication?

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

Which of the following enzymes is involved in relieving DNA supercoiling during DNA replication?