Unit 6: Gene Expression and Regulation

Vocabulary flashcards cover major terms, molecules, enzymes, processes, regulatory elements, mutations, and biotechnology techniques essential to understanding Unit 6 of AP Biology: Gene Expression and Regulation.

Gene

A DNA sequence that codes for a functional product (RNA or protein) and is inherited as a discrete unit.

Allele

Alternative form of a gene that occupies the same locus and produces variation in a trait.

DNA (Deoxyribonucleic Acid)

Primary hereditary molecule composed of deoxyribose, phosphate groups, and nitrogenous bases (A, T, C, G).

RNA (Ribonucleic Acid)

Single-stranded nucleic acid containing ribose and uracil; participates in gene expression.

Purine

Double-ring nitrogen base (adenine or guanine).

Pyrimidine

Single-ring nitrogen base (cytosine, thymine, or uracil).

Plasmid

Small circular, double-stranded DNA molecule found in bacteria and some eukaryotes; often carries extra genes.

Semiconservative Replication

DNA replication mechanism in which each new double helix contains one parental and one newly synthesized strand.

Helicase

Enzyme that unwinds and separates DNA strands at the replication fork.

Topoisomerase

Enzyme that relieves supercoiling ahead of the replication fork.

DNA Polymerase

Enzyme that adds nucleotides to a growing DNA strand in the 5′ → 3′ direction.

RNA Primer

Short RNA segment synthesized by primase to initiate DNA replication.

Leading Strand

DNA strand synthesized continuously toward the replication fork.

Lagging Strand

DNA strand synthesized discontinuously away from the fork as Okazaki fragments.

Ligase

Enzyme that joins Okazaki fragments by forming phosphodiester bonds.

Template (Antisense) Strand

DNA strand read by RNA polymerase to synthesize complementary mRNA.

mRNA (Messenger RNA)

RNA molecule that carries genetic information from DNA to the ribosome.

tRNA (Transfer RNA)

Adapter RNA that carries specific amino acids and contains an anticodon to pair with mRNA codons.

rRNA (Ribosomal RNA)

Structural and catalytic RNA component of ribosomes.

Codon

Three-nucleotide mRNA sequence that specifies an amino acid or stop signal.

Anticodon

Three-nucleotide tRNA sequence complementary to an mRNA codon.

Start Codon

AUG sequence that initiates translation and codes for methionine.

Stop Codon

UAA, UAG, or UGA sequence that terminates translation.

Genetic Code

Universal, nearly unambiguous set of codon-to-amino-acid correspondences.

Transcription

Process in which RNA polymerase synthesizes RNA from a DNA template.

RNA Polymerase

Enzyme that builds RNA strands by reading DNA 3′ → 5′.

Poly-A Tail

Series of adenine nucleotides added to 3′ end of eukaryotic mRNA for stability and export.

GTP Cap (5′ Cap)

Modified guanine nucleotide added to 5′ end of eukaryotic mRNA for protection and ribosome binding.

Intron

Noncoding RNA segment removed during RNA processing.

Exon

Coding sequence retained in mature mRNA.

Alternative Splicing

Process that combines exons in different ways to produce multiple mRNA variants from one gene.

Translation

Synthesis of a polypeptide using mRNA information at a ribosome.

Retrovirus

RNA virus that uses reverse transcriptase to copy RNA into DNA for integration into host genome.

Reverse Transcriptase

Enzyme that synthesizes complementary DNA from an RNA template.

Operon

Cluster of prokaryotic genes under control of a single promoter and regulatory elements.

lac Operon

Inducible operon in E. coli that controls genes for lactose metabolism; activated in presence of lactose, low glucose.

Promoter

DNA sequence where RNA polymerase binds to start transcription.

Regulatory Sequence

DNA segment (e.g., enhancer, operator) that interacts with proteins to control gene expression.

Transcription Factor

Protein that binds DNA regulatory sequences to increase or decrease transcription.

Epigenetic Modification

Heritable, reversible change (e.g., DNA methylation, histone acetylation) that affects gene expression without altering DNA sequence.

Differential Gene Expression

Selective activation of genes resulting in distinct cell types and functions.

Mutation

Permanent change in DNA nucleotide sequence.

Point Mutation

Single-base substitution in DNA.

Frameshift Mutation

Insertion or deletion not in multiples of three, altering downstream reading frame.

Silent Mutation

Point mutation that does not change amino acid sequence due to genetic code redundancy.

Missense Mutation

Point mutation that changes one amino acid in a protein.

Nonsense Mutation

Point mutation converting a codon into a stop codon, truncating the protein.

Polyploidy

Condition of having more than two complete sets of chromosomes.

Transformation (Horizontal Transfer)

Uptake of naked DNA by prokaryotic cells, increasing genetic variation.

Transduction

Transfer of DNA between bacteria via bacteriophages.

Conjugation

Direct DNA transfer between bacterial cells through a pilus.

Transposition

Movement of DNA segments within or between molecules via transposable elements.

PCR (Polymerase Chain Reaction)

Technique that amplifies specific DNA fragments exponentially in vitro.

Gel Electrophoresis

Method that separates DNA, RNA, or proteins based on size/charge in an electric field.

DNA Sequencing

Laboratory process that determines the precise order of nucleotides in DNA.

Bacterial Transformation

Introduction of recombinant plasmids into bacteria for cloning or expression.

Genetically Modified Organism (GMO)

Organism whose genome has been altered using biotechnology techniques.