D1.1 DNA Replication and PCR – Vocabulary

Vocabulary flashcards covering key terms from the lecture notes on DNA replication, base pairing, enzymes, PCR, and gel electrophoresis.

DNA Replication

The process of making exact copies of DNA; produces identical base sequences to the original and enables reproduction, growth, and repair.

Semi-Conservative Replication

Each new DNA molecule contains one original (parental) strand and one newly synthesized strand.

Complementary Base Pairing

A-T and C-G pairing that guides the precise assembly of new DNA strands.

Helicase

Enzyme that unwinds the DNA double helix by breaking hydrogen bonds, creating the replication fork.

DNA Polymerase III

Main enzyme for DNA synthesis; adds nucleotides in the 5′→3′ direction and Proofreads; handles leading (continuous) and lagging (discontinuous) synthesis.

DNA Polymerase I

Removes RNA primers and replaces them with DNA nucleotides.

DNA Primase

RNA polymerase that synthesizes short RNA primers on the DNA template to start replication.

Primers

Short DNA/RNA sequences that bind to target regions to mark the starting points for replication.

Taq Polymerase

Heat-stable DNA polymerase used in PCR to synthesize new DNA strands.

Phosphodiester Bond

Bond between adjacent nucleotides; forms the backbone of DNA by linking 5′ phosphate to 3′ hydroxyl.

Replication Fork

Y-shaped region where the DNA double helix is unwound and new strands are made.

Leading Strand

DNA strand synthesized continuously toward the replication fork; typically needs only one RNA primer.

Lagging Strand

DNA strand synthesized discontinuously away from the fork in short Okazaki fragments, with multiple RNA primers.

Okazaki Fragments

Short DNA fragments formed on the lagging strand and later joined into a continuous strand by DNA ligase.

Directionality of DNA Synthesis

DNA polymerases add nucleotides to the 3′ end, so synthesis proceeds in the 5′→3′ direction.

Antiparallel

The two DNA strands run in opposite directions (one 5′→3′, the other 3′→5′).

DNA Ligase

Enzyme that seals gaps between Okazaki fragments, forming continuous phosphodiester bonds.

Denaturation (PCR Step)

Heating to about 95°C to separate DNA strands by breaking hydrogen bonds.

Annealing (PCR Step)

Cooling to about 50–65°C to allow primers to bind to target DNA sequences.

Extension (PCR Step)

Around 72°C for the synthesis of new DNA strands by extending from primers.

PCR (Polymerase Chain Reaction)

Technique to amplify a specific DNA segment using primers, Taq polymerase, and thermal cycling.

Gel Electrophoresis

Technique that separates DNA fragments by size as they migrate through a gel under an electric field.

DNA Profiling

Using DNA markers to identify individuals (forensics), determine paternity, diagnose diseases, and study populations; reliability improves with more markers.

Mismatch Proofreading (DNA Polymerase III)

DNA polymerase III proofreads and corrects mismatches via 3′→5′ exonuclease activity, backtracking, and replacement.