D1.1 DNA Replication HL

Vocabulary flashcards covering the molecular mechanisms of semi-conservative DNA replication, replication enzymes, leading and lagging strand synthesis, DNA proofreading, and laboratory applications including PCR and gel electrophoresis.

DNA Replication

The biological process that produces exact copies of DNA with identical base sequences, required for reproduction, growth, and tissue replacement in multicellular organisms.

Semi-Conservative Replication

A style of replication in which each newly formed DNA molecule consists of one original template strand and one newly synthesized strand, conserving half of the original DNA.

DNA Helicase

An enzyme that unwinds the double helix and breaks the hydrogen bonds between complementary strands of DNA.

Gyrase

A protein that stabilizes the DNA and works together with single-stranded binding proteins to hold the DNA open for replication.

Single-Strand Binding Proteins

Proteins that stabilize the unwound parental DNA strands and keep them held open during replication.

DNA Primase

An enzyme that synthesizes and adds a short RNA primer to both template DNA strands to initiate DNA synthesis.

DNA Polymerase III

An enzyme that adds DNA nucleotides starting at the primer via complementary base pairing by reading the template strand in the $3'$ to $5'$ direction and building the new strand in the $5'$ to $3'$ direction.

DNA Polymerase I

An enzyme that removes the RNA primer and replaces it with DNA nucleotides.

DNA Ligase

An enzyme that joins fragments of DNA together by forming covalent bonds along the phosphodiester backbone between the phosphate group and the $3'$ carbon.

Leading Strand

The strand of nascent DNA that is synthesized continuously in the $5' \rightarrow 3'$ direction toward the replication fork.

Lagging Strand

The strand of nascent DNA that is synthesized discontinuously in short segments away from the replication fork.

Okazaki Fragments

Short discontinuous segments of DNA synthesized on the lagging strand that are later joined together by DNA ligase.

DNA Proofreading

A process in which DNA polymerase detects mispaired bases, removes the incorrect nucleotide from the $3'$ terminal using $3' \rightarrow 5'$ exonuclease activity, and replaces it with the correctly matched nucleotide.

Polymerase Chain Reaction (PCR)

A molecular biology technique used to make billions of copies of a targeted DNA region from a template strand using cyclic temperature changes.

Taq Polymerase

A heat-stable DNA polymerase derived from thermophilic bacteria that is activated around $70^\times\text{C}$ to $72^\times\text{C}$ to synthesize new DNA strands during PCR.

Primers (in PCR)

Short nucleotide sequences added to a PCR mixture that attach to template DNA at $54^\times\text{C}$ to ensure only the targeted region is amplified.

dNTPs (Deoxynucleotide Triphosphates)

Free nucleotide building blocks added to a PCR mixture that are utilized by Taq polymerase to construct the new DNA strands.

Gel Electrophoresis

A technique where amplified DNA is loaded into the wells of a gel and separated by fragment size using an applied electric current.

Single Nucleotide Polymorphisms (SNPs)

Specific sequence variations analyzed in forensic science, typically testing around $30$ different loci to produce reliable DNA profiles for crime scene analysis.