Comprehensive DNA, RNA, and Gene Regulation Key Terms for Biology

Antiparallel

Describes the opposite orientation of the two DNA strands, where one runs 5′→3′ and the other runs 3′→5′, allowing complementary base pairing and proper functioning of enzymes.

Plasmid

A small, circular DNA molecule found in bacteria that replicates independently of the chromosome and often carries genes for antibiotic resistance or other traits.

Purine

A type of nitrogenous base with a double-ring structure; adenine (A) and guanine (G) are ____________.

Pyrimidine

A nitrogenous base with a single-ring structure; cytosine (C), thymine (T), and uracil (U) are _________.

DNA Replication

the biological process where a single DNA molecule is duplicated to produce two identical DNA molecules.

DNA ligase

The enzyme that seals breaks in the sugar-phosphate backbone, joining Okazaki fragments to make a continuous DNA strand.

DNA polymerase

The enzyme that adds new nucleotides to a growing DNA strand during replication and also proofreads for mistakes.

DNA primase

The enzyme that builds short RNA primers, which provide starting points for DNA polymerase.

Semiconservative

Describes DNA replication in which each new DNA molecule contains one original strand and one newly synthesized strand.

Leading strand

The DNA strand synthesized continuously in the 5′→3′ direction toward the replication fork.

Lagging strand

The DNA strand synthesized in short, discontinuous segments away from the replication fork.

Okazaki fragment

Short DNA segments produced on the lagging strand during replication.

Topoisomerase

An enzyme that relieves tension created by unwinding DNA by cutting and rejoining the strands.

Alternative splicing

A process in eukaryotes where different combinations of exons are joined together, allowing one gene to produce multiple proteins.

Anticodon

A three-base sequence on a tRNA molecule that pairs with a codon on mRNA during translation.

Codon

A three-nucleotide sequence on mRNA that specifies an amino acid or a stop signal.

Exon

The coding region of a gene that remains in the final mRNA and is translated into protein.

Intron

A noncoding region of a gene that is removed from pre-mRNA during RNA processing.

mRNA

Messenger RNA; carries the genetic code from DNA to the ribosome for protein synthesis.

Promoter

A DNA sequence where RNA polymerase binds to begin transcription.

Reverse transcriptase

An enzyme used by retroviruses to convert RNA into DNA, which can then integrate into the host genome.

rRNA

Ribosomal RNA; a main component of ribosomes that helps catalyze peptide bond formation.

RNA polymerase

The enzyme that builds RNA strands by reading a DNA template during transcription.

Transcription

The process of copying DNA into RNA, carried out by RNA polymerase.

Translation

The process where ribosomes read mRNA and assemble amino acids into a protein.

tRNA

Transfer RNA; brings amino acids to the ribosome and matches them to codons using its anticodon.

Conjugation

A form of bacterial gene transfer where DNA is passed directly from one bacterium to another through a pilus.

Deletion

A mutation where one or more nucleotides or entire chromosome sections are removed.

Duplication

A mutation where a segment of DNA or a chromosome is copied, resulting in extra genetic material.

Frameshift

A mutation caused by insertion or deletion of nucleotides that changes the reading frame of the codons.

Inversion

A mutation where a chromosome segment breaks off, flips, and reattaches in the reverse orientation.

Mutagen

A physical or chemical agent that increases the rate of mutations (e.g., UV light, radiation).

Silent mutation

A substitution that changes a nucleotide but does not change the amino acid due to redundancy in the genetic code.

Missense mutation

A substitution that changes one amino acid in the protein sequence.

Nonsense mutation

A substitution that changes a codon into a stop codon, leading to a shortened protein.

Substitution (point mutation)

A mutation where one nucleotide is replaced by another.

Transduction

Transfer of bacterial genes by a virus (bacteriophage).

Transformation

Uptake of naked DNA from the environment by bacteria.

Translocation

A mutation where a piece of one chromosome breaks off and attaches to a different chromosome.

Transposition

Movement of "jumping genes" (transposons) from one location in the genome to another.

Gene Regulation

Epigenetics

Heritable changes in gene activity that do not involve changes in DNA sequence, often caused by DNA methylation or histone modification.

Operator

A DNA segment in prokaryotic operons where a repressor can bind to block transcription.

Operon

A group of genes under one promoter in bacteria, allowing coordinated regulation of related functions.

Repressor

A protein that binds to an operator to block RNA polymerase and stop transcription.

RNA interference (RNAi)

A biological process where small RNAs (siRNA or miRNA) silence gene expression by degrading mRNA or blocking translation.

Transcription factor

A protein that binds to DNA to promote or inhibit the start of transcription in eukaryotes.

Gel electrophoresis

A technique that separates DNA, RNA, or proteins based on size by running them through a gel with an electric current.

Polymerase chain reaction (PCR)

A method used to amplify a specific segment of DNA, producing millions of copies quickly.

Restriction enzyme

A bacterial enzyme that cuts DNA at specific sequences, used in cloning and DNA analysis.