DNA Structure and Replication

Vocabulary flashcards covering the molecular structure of DNA, nucleotide pairings, groove anatomy, replication models, and the enzymes involved in DNA synthesis.

Purines

Nitrogenous bases containing a two-ring structure, specifically represented by adenine and guanine in nucleic acids.

Pyrimidines

Nitrogenous bases consisting of a single six-sided ring, including cytosine and thymine in DNA, and cytosine and uracil in RNA.

Double Helix

The structural conformation of a DNA molecule, consisting of two helical strands wound around each other.

Phosphodiester Bond

A covalent linkage formed by a phosphate group and two esters that joins the five prime carbon of one nucleotide to the three prime carbon of the adjacent nucleotide.

Sugar-Phosphate Backbone

The repeating phosphate-sugar structural chain of a single DNA strand that features a distinct five prime end and three prime end.

Complementary Base Pairs

Specific pairs of nitrogenous bases held together by hydrogen bonds, where adenine always pairs with thymine via two hydrogen bonds, and guanine pairs with cytosine via three hydrogen bonds.

Antiparallel

The relative orientation of the two complementary strands in a DNA molecule running in opposite directions, with one oriented five prime to three prime and the other oriented three prime to five prime.

Major Groove

The wider groove of the DNA double helix, formed because sugars extend at approximately a $120^\circ$ angle, which serves as the binding region for proteins that recognize specific nucleotide sequences.

Minor Groove

The narrower groove along the DNA double helix where proteins bind nonspecifically to any sequence of DNA.

Conservative Replication

A hypothesized model of DNA replication where the original parental DNA molecule remains completely intact and conserved as a unit while directing the synthesis of an entirely new molecule.

Semiconservative Replication

The confirmed model of DNA replication in which each newly formed DNA molecule consists of one conserved parental strand and one newly synthesized strand.

Dispersive Replication

A hypothesized model of DNA replication proposing that parental and daughter DNA segments are interspersed throughout both strands of the replicated molecules.

Isotope

Atoms of the same chemical element that have an identical number of protons and electrons but differ in their number of neutrons, resulting in different atomic masses.

Meselson and Stahl Experiment

An experiment that cultured E. coli in heavy $^{15}\text{N}$ media before transferring them to normal $^{14}\text{N}$ media and using centrifugation density separation to prove that DNA replicates semiconservatively.

Deoxynucleotide Triphosphates (dNTPs)

Monomer building blocks for DNA synthesis containing three phosphate groups that provide the chemical energy needed to form phosphodiester bonds in a growing strand.

DNA Polymerase

The enzyme that synthesizes new DNA strands in the five prime to three prime direction by matching incoming complementary nucleotides to a parent template strand and adding them to an existing three prime end.

RNA Primer

A short sequence of RNA synthesized by an RNA polymerase that provides the necessary free three prime end required for DNA polymerase to initiate strand synthesis.