DNA Replication

Practice flashcards covering the concepts, mechanisms, and key enzymes of DNA replication, including the Meselson-Stahl experiment and DNA packaging.

Storage of Information

One of the four crucial characteristics a molecule must exhibit to serve as genetic material.

Replication

One of the four crucial characteristics of genetic material; specifically the process of producing semi-conservatively replicated daughter strands.

Expression of Information

One of the four crucial characteristics a molecule must exhibit to serve as genetic material.

Variation by mutation

One of the four crucial characteristics a molecule must exhibit to serve as genetic material.

Central Dogma

The concept that "DNA makes RNA, which makes proteins."

Semiconservative replication model

A model of DNA replication that results in two hybrid molecules, each containing one old strand and one newly synthesiszed strand.

Conservative model

A model of DNA replication that results in one entirely new molecule and conserves the old molecule.

Dispersive model

A model of DNA replication that results in hybrid molecules where each strand is a mixture of old and new DNA.

Meselson-Stahl (1958) Experiment

An experiment that used a heavy isotope of nitrogen ($^{15}N$) and centrifugation to prove that DNA replication is semiconservative.

$15NH_4Cl$ (Ammonium Chloride)

The only nitrogen source provided to bacterial cells in the Meselson-Stahl experiment to ensure DNA was made of "heavy nitrogen."

Pyrimidines

Single-ringed organic bases found in nucleic acids.

Purines

Double-ringed organic bases found in nucleic acids.

$\beta$-N-glycosidic bond

The bond that attaches nitrogenous bases to the $1'C$ of the sugar in a nucleotide.

Autonomously replicating sequence (ARS)

AT-rich sequences that serve as the initiation sites of DNA replication in prokaryotic genomes.

Origin recognition complex (ORC)

A six-protein complex that recognizes replication origins in eukaryotes during the early G1 phase of the cell cycle.

DNA Polymerase III

The enzyme in prokaryotes that adds DNA nucleotides to the RNA primer and proofreads added bases.

DNA Polymerase I

The enzyme that replaces the RNA primer and fills the gaps between Okazaki fragments.

Topoisomerase

An enzyme that unwinds DNA to solve topological problems caused by replication.

DNA Helicase

An enzyme that separates polynucleotide strands of DNA by breaking hydrogen bonds.

Single-stranded binding proteins (SSBP)

Proteins that attach to polynucleotides to prevent the reattachment of separated strands and maintain stability.

Primase

An enzyme that makes a short segment of RNA, called a primer, which is complementary to the DNA.

Leading Strand

The DNA strand synthesized continuously in the $5' \rightarrow 3'$ direction.

Lagging Strand

The DNA strand synthesized in segments called Okazaki fragments in the $5' \rightarrow 3'$ direction.

Okazaki fragments

Discontinuous $5' \rightarrow 3'$ DNA segments produced during the synthesis of the lagging strand.

DNA Ligase

An enzyme that joins Okazaki fragments by forming a covalent phosphodiester linkage between $3'$-hydroxyl and $5'$-phosphate groups.

Proofreading

The $3' \rightarrow 5'$ exonuclease activity of DNA polymerase that removes incorrectly inserted nucleotides from the $3'$ end.

Telomerase

An enzyme that maintains the ends of linear DNA molecules (telomeres) to ensure they do not shorten with every round of replication.

Chromatin

The complex of DNA and proteins that makes up a chromosome.

Histones

DNA-binding proteins that help compact and fold DNA into chromosomes.

Nucleosome

A structure within chromosomes where DNA is coiled around clusters of histones.