DNA replication glossary

Conservation (of sequences)

When a base sequence in a DNA molecule (or an a.a. sequence in a protein) has remained unchanged throughout evolution.

DNA ligase

Enzyme that joins the ends of two strands of DNA together with a covalent bond to produce one continuous DNA strand.

DNA polymerase

Enzyme that synthesizes DNA by joining nucleotides together using a DNA template as a guide; its substrates are the four nucleoside triphosphates: A G C T

DNA helicase

Enzyme that harnesses ATP hydrolysis energy to open a region of the DNA helix into its single strands as an aid to DNA replication or DNA repair.

DNA primase

Enzymes that synthesizes a short strand of RNA on a DNA template, producing an RNA primer for DNA synthesis (landing platform for DNA polymerase)

Double strand break

The phosphodiester bond between two nucleotides is broke, leading to the double helix to become 2 independent pieces.

Evolution

The process by which different kinds of living organism are believed to have developed from earlier forms during the history of the earth

Fidelity

The degree of exactness with which something is copied or reproduced

Genetic Variation

the difference in DNA sequences between individuals within a populatio

Leading strand

One of the two newly synthesized strands of DNA found at a replication fork. The leading strand is made by continuous synthesis in the 5′-to-3′ direction

Lagging strand

One of the two newly synthesized strands of DNA found at a replication fork. The lagging strand is made in discontinuous lengths that are later joined covalently

Mutation

Heritable change in the nucleotide sequence of a chromosome (more appropriate use of word is variant)

Origin of replication

A location on a DNA molecule at which duplication of the DNA begins by the formation of replication forks

Okazaki fragments

Short pieces of DNA formed on the lagging strand of the replication fork in a discontinuous manner because all known DNA polymerases work in a 5′→3′ direction

Proofreading

In DNA synthesis the ability of DNA polymerase to recognise mismatched bases, the mechanism for checking the intended amino acid is incorporated into a polypeptide chain

Replication fork

Y-shaped region of a replicating DNA molecule; the point at which the two strands of the parent

DNA helix are being separated and the daughter strands are being formed

RNA primer

Short stretch of RNA synthesized on a DNA template. It is required by DNA polymerases to start their DNA synthesis

Single stranded binding proteins (SSBP)

Protein that binds to the single strands of the opened-up DNA double helix, preventing helical structures from re-forming while the DNA is being replicated

Topoisomerase (includes DNA Gyrase)

Enzyme that binds to DNA and reversibly breaks a phosphodiester bond in one or both strands. Topoisomerase I creates transient single-strand breaks, allowing the double helix to swivel and relieving superhelical tension. Topoisomerase II creates transient double-strand breaks, allowing one double helix to pass through another and thus resolving knots and tangles

Variant

A gene variant is a permanent change in the DNA sequence that makes up a gene. This type of genetic change used to be known as a gene mutation, but because changes in DNA do not always cause disease, it is thought that gene variant is a more accurate term