DNA Structure and Replication

Flashcards for key concepts related to DNA structure and replication, designed for exam review.

Helix

A three-dimensional spiral shape, such as that formed by a DNA molecule.

Antiparallel

Refers to the opposite direction of the two strands of DNA, with one strand running 5' to 3' and the other 3' to 5'.

Purines

Nitrogenous bases including adenine and guanine, which have a double-ring structure.

Pyrimidines

Nitrogenous bases including cytosine and thymine, which have a single-ring structure.

Hydrogen Bonds

Weak interactions that occur between complementary bases in DNA: adenine pairs with thymine (two hydrogen bonds), and guanine pairs with cytosine (three hydrogen bonds).

Phosphate Group

A chemical group (PO4) that connects sugar molecules in the DNA backbone.

DNA Polymerase

The enzyme responsible for synthesizing new DNA strands by adding nucleotides to a pre-existing strand.

Dehydration Synthesis

A chemical reaction that joins molecules by the removal of water (H2O), used in forming bonds in DNA.

Semi-conservative Replication

The method of DNA replication where each new DNA molecule consists of one old strand and one new strand.

Okazaki Fragments

Short segments of DNA synthesized on the lagging strand during DNA replication.

Leading Strand

The strand of DNA that is continuously synthesized in the same direction as the replication fork opens.

Lagging Strand

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

Primase

An enzyme that synthesizes a short RNA primer for DNA polymerase to extend.

Ligase

The enzyme responsible for joining Okazaki fragments on the lagging strand by forming covalent bonds.

Templates

The original DNA strands that guide the synthesis of new complementary strands during replication.

Single-Stranded Binding Proteins (SSBPs)

Proteins that prevent the re-annealing of DNA strands during replication.

Replication Fork

The Y-shaped region where the DNA double helix is unwound and replication is occurring.