DNA Structure, Replication, and Gene Expression: Eukaryotic and Prokaryotic Mechanisms

Nucleotides

Building blocks of DNA (phosphate group, deoxyribose sugar, nitrogenous base).

Adenine (A) Thymine (T) Cytosine (C) Guanine (G)

One of the nitrogenous bases in DNA.

Phosphodiester bonds

Covalent bonds that form the sugar-phosphate backbone of DNA.

Hydrogen bonds

Bonds that hold complementary bases together (A-T = 2 H bonds, C-G = 3 H bonds).

Double helix

Shape of DNA with antiparallel strands.

Directionality of DNA strands

Each strand runs 5' → 3'.

DNA vs. RNA

DNA has deoxyribose, thymine, double-stranded; RNA has ribose, uracil, usually single-stranded.

Helicase

Enzyme that unwinds the DNA double helix during replication.

Single-strand binding proteins

Proteins that stabilize separated strands of DNA.

Primase

Enzyme that lays down RNA primers during DNA replication.

DNA polymerase

Enzyme that adds nucleotides in the 5' → 3' direction during DNA replication.

Leading strand

Strand synthesized continuously during DNA replication.

Lagging strand

Strand synthesized discontinuously (Okazaki fragments) during DNA replication.

DNA polymerase I

Enzyme that replaces RNA primers with DNA.

DNA ligase

Enzyme that seals gaps between DNA fragments.

Gene expression

Process by which information from a gene produces a functional product (protein or RNA).

Transcription

Synthesis of RNA from a DNA template.

Translation

Synthesis of a polypeptide using an mRNA template.

5' cap

Added for protection and ribosome binding during RNA modification.

Poly-A tail

Added to 3' end of RNA for stability.

RNA splicing

Process of removing introns and joining exons in RNA.

Point mutations

Types of mutations in DNA sequence including substitution, deletion, and insertion

Frameshift mutations

Insertions or deletions that shift the reading frame of DNA.