DNA Replication and Repair

These flashcards cover key terms and concepts related to DNA replication and repair, as outlined in the lecture notes.

Semiconservative DNA replication

A method of DNA replication where each new DNA molecule contains one strand from the original molecule and one newly synthesized strand.

Leading strand

The DNA strand that is synthesized continuously in the 5' to 3' direction as the replication fork advances.

Lagging strand

The DNA strand that is synthesized discontinuously in short segments known as Okazaki fragments, moving away from the replication fork.

Okazaki fragments

Short sequences of DNA produced during the synthesis of the lagging strand and later joined together by DNA ligase.

DNA polymerase III

The primary enzyme responsible for DNA synthesis in bacteria, synthesizing new DNA strands by adding nucleotides to a growing chain.

Helicase

An enzyme that unwinds the DNA double helix at the replication fork, breaking hydrogen bonds between the base pairs.

Nucleotide Excision Repair (NER)

A DNA repair mechanism that removes bulky lesions from DNA, caused mainly by environmental mutagens.

Base Excision Repair (BER)

A DNA repair process that corrects altered nucleotides caused by reactive chemicals or metabolism.

Mismatch Repair (MMR)

The DNA repair mechanism that corrects mistakes made during DNA replication that escape the proofreading ability of DNA polymerases.

Double Strand Break (DSB) repair

A process of DNA repair that can occur through nonhomologous end joining (NHEJ) or homologous recombination.

DNA replication fork

The area where the DNA double helix is unwound and separated during the process of replication.

RNA primer

A short strand of RNA that is synthesized by primase to initiate DNA replication, providing a starting point for DNA polymerase.

Primase

An enzyme that synthesizes a short RNA primer complementary to the DNA template to allow DNA polymerase to start DNA synthesis.

DNA ligase

An enzyme that joins Okazaki fragments together on the lagging strand by forming phosphodiester bonds between adjacent nucleotides.

Topoisomerase

An enzyme that alleviates the torsional strain caused by the unwinding of the DNA helix during replication.