Passage
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) , a nonpolar analog that lacks Watson-Crick hydrogen bonding. Klenow fragment (KF) polymerase, which has 3′-5′ but not 5′-3′ exonuclease activity, was incubated with a mixture of DNA template, primers, and dNTPs, including dFTP derivatives. 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 enzyme
Adapted 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.
-Which of the following would NOT be present in the structure of the dFTP nucleotide used for replication?

Question

Passage
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) , a nonpolar analog that lacks Watson-Crick hydrogen bonding. Klenow fragment (KF) polymerase, which has 3′-5′ but not 5′-3′ exonuclease activity, was incubated with a mixture of DNA template, primers, and dNTPs, including dFTP derivatives. 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 enzyme
Adapted 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.
-Which of the following would NOT be present in the structure of the dFTP nucleotide used for replication?

Quizplus · Accepted Answer

11ecba2d_0e9d_7f57_a3bf_6310305c86ac_MD0008_00 Deoxyribonucleotides are the monomer units that make up the structure of DNA. A nucleotide is composed of a nucleoside molecule attached by a phosphoester bond to one or more phosphate groups. Nucleosides consist of a pentose (five-carbon) sugar linked to a nitrogenous base on the 1′ carbon by a covalent glycosidic bond. Ribose and deoxyribose are the two types of pentose sugars used in nucleotide production, and only differ in structure at the 2′ carbon. Ribose sugars have a hydroxyl group at the 2′ carbon where deoxyribose sugars have a hydrogen atom. DNA replication only utilizes nucleotides that contain deoxyribose sugars. To create dNTP derivatives of dFTP, researchers substituted thymine bases with difluorotoluene. Because the remaining nucleotide structure is unaltered, dFTP nucleotides would not contain hydroxyl groups on the 2′ carbon of the pentose sugar. (Choice A) Deoxyribonucleotides, including those made with dFTP, all contain phosphate groups on the 5′ carbon of the pentose sugar. (Choice B) All nucleotides and nucleosides are bonded to nitrogenous bases at the 1′ carbon of the pentose sugar through a glycosidic bond, which is a bond between a carbohydrate and any other group. (Choice D) The H group on the 5′ carbon of the pentose sugar is present in nucleosides and nucleotides. Educational objective: A nucleoside is a pentose (five-carbon) sugar linked to a nitrogenous base on the 1′ carbon by a covalent glycosidic bond. Nucleotides consist of a nucleoside attached to one or more phosphate groups by a phosphoester bond. If the pentose has a hydroxyl group at the 2′ carbon, it is ribose; if a hydrogen is present at the same position, it is deoxyribose.

Passage DNA Polymerization Is One of the Most Conserved Mechanisms of of Genome