DNA Structure and Replication

DNA Double Helix

the physical structure of DNA, resembling a twisted ladder, composed of two antiparallel, complementary polynucleotide strands

Sugar Phosphate Backbone

the structural framework of DNA and RNA, composed of alternating sugar (deoxyribose in DNA, ribose in RNA) and phosphate groups linked by covalent phosphodiester bonds

5’-3’ Synthesis

the mandatory, universal process in which DNA and RNA polymerase enzymes build nucleic acid strands by adding new nucleotides exclusively to the 3' hydroxyl (-OH) end

Complementary Base Pairing

the specific, predictable binding of nitrogenous bases in DNA and RNA

Hydrogen Bonding Between Bases

weak, intermolecular forces that hold the two strands of the DNA double helix together, allowing them to separate for replication and transcription

Replication

the biological process of creating an exact copy of a DNA molecule, ensuring genetic continuity during cell division

Origin of Replication

a specific DNA sequence where replication begins, characterized by AT-rich regions that are easily unwound

Semi-conservative Model

each of the two parental DNA strands acts as a template for new strand synthesis, resulting in two DNA molecules that each contain one original (conserved) strand and one newly synthesized strand

DNA Polymerase

an essential enzyme that synthesizes new DNA molecules by assembling nucleotides, the building blocks of DNA, during replication and repair

DNA Ligase

essential enzyme that repairs and seals nicks in DNA by catalyzing the formation of phosphodiester bonds between adjacent 3′-hydroxyl and 5′-phosphate termini

Helicase

essential motor proteins that use energy from ATP hydrolysis to separate double-stranded nucleic acids (DNA or RNA) into single strands, playing critical roles in DNA replication, repair, and transcription

Topoisomerase

essential enzymes that regulate DNA topology by breaking and resealing DNA strands to relieve topological strain (supercoiling) during replication and transcription

Anti-parallel

two parallel lines or molecular strands that run in opposite directions or orientations, commonly seen in the 5′→3′ and 3′→5′ orientation of DNA strands

Okazaki Fragments

short, discontinuously synthesized DNA sequences (1000–2000 nucleotides in bacteria, 100–200 in eukaryotes) that form the lagging strand during DNA replication

Leading and Lagging Strands

The leading strand requires one primer, while the lagging strand needs multiple primers, making its synthesis slower

Major and Minor Groove

structural features of the DNA double helix formed by the asymmetrical pairing of bases and the backbone, providing binding sites for proteins

DNA Binding Protein

diverse proteins that physically interact with DNA, regulating crucial cellular processes like transcription, replication, repair, and chromatin organization