Part 1~Bio (DNA Structure & Replication)

DNA Nucleotides

Composed of a phosphate group, deoxyribose sugar, and a nitrogenous base (Adenine, Thymine, Guanine, Cytosine).

Adenine (A)

A nitrogenous base that pairs with Thymine (T) via 2 hydrogen bonds. It is a purine.

Thymine (T)

A nitrogenous base that pairs with Adenine (A) via 2 hydrogen bonds. It is a pyrimidine.

Guanine (G)

A nitrogenous base that pairs with Cytosine (C) via 3 hydrogen bonds. It is a purine.

Cytosine (C)

A nitrogenous base that pairs with Guanine (G) via 3 hydrogen bonds. It is a pyrimidine.

DNA Backbone

Composed of alternating deoxyribose sugars and phosphate groups, linked by phosphodiester bonds.

Double Helix Structure

Composed of antiparallel strands oriented from 5′ to 3′ and 3′ to 5′, with complementary base pairing.

DNA Replication

A semiconservative process where each new DNA molecule consists of one old strand and one new strand.

Helicase

An enzyme that unwinds the double helix structure of DNA during replication.

Topoisomerase

An enzyme that relieves the strain on the DNA molecule while unwinding during replication.

Primase

An enzyme that adds RNA primers, which are necessary for DNA polymerase to begin synthesis.

DNA Polymerase III

An enzyme that synthesizes new DNA strands in a 5′ to 3′ direction.

DNA Polymerase I

An enzyme that replaces RNA primers with DNA nucleotides.

Ligase

An enzyme that seals the gaps between Okazaki fragments on the lagging strand.

Leading Strand

Continuously synthesized in the 5′ to 3′ direction during DNA replication.

Lagging Strand

Synthesized discontinuously in segments, known as Okazaki fragments, during DNA replication.

Okazaki Fragments

Short sequences of DNA nucleotides synthesized on the lagging strand during DNA replication, which must be joined by DNA ligase to form a continuous strand.