DNA and the Genome – Key Terms (Higher Biology)

Vocabulary flashcards covering core terms related to DNA structure, replication, transcription/translation, genome organization, mutations, evolution, and genomic technologies.

Nucleotide

A basic unit of DNA composed of a deoxyribose sugar, a phosphate group, and a nitrogenous base.

Deoxyribose sugar

Five-carbon sugar present in DNA nucleotides; forms part of the backbone.

Phosphate group

Phosphate component of a nucleotide; links with sugars to form the sugar–phosphate backbone.

Base

Nitrogenous base (adenine, thymine, guanine, cytosine) attached to the sugar in a nucleotide.

Adenine

Purine base that pairs with thymine in DNA (A–T base pair).

Thymine

Pyrimidine base that pairs with adenine in DNA (T–A base pair). Note: replaced by uracil in RNA.

Guanine

Purine base that pairs with cytosine in DNA (G–C base pair).

Cytosine

Pyrimidine base that pairs with guanine in DNA (C–G base pair).

Base pairing

Specific pairing of bases (A–T and G–C in DNA) via hydrogen bonds.

Complementary base pairing

A–T and G–C pairing that allows two DNA strands to fit together.

Double helix

Structure of DNA where two strands coil around each other, forming a twisted ladder.

Antiparallel

Orientation of the two DNA strands: one runs 5' to 3', the other 3' to 5'.

5' end

Phosphate end of a DNA strand; the 5' carbon of the sugar is exposed.

3' end

Hydroxyl end of a DNA strand; the 3' carbon of the sugar is exposed.

Sugar-phosphate backbone

The repeating linkage of sugar and phosphate groups that forms the strands' framework.

Prokaryote

Single-celled organism without a nucleus; DNA is usually circular and free in the cytoplasm.

Eukaryote

Organism with a nucleus and linear chromosomes; DNA is associated with histones.

Plasmid

Small circular DNA molecule in prokaryotes that carries extra genes; can be exchanged between cells.

Mitochondrial DNA

Circular DNA found in mitochondria; evidence for endosymbiotic origin.

Chloroplast DNA

Circular DNA in chloroplasts; evidence for endosymbiotic origin.

DNA replication

Semi-conservative process by which a cell copies its DNA before division.

DNA polymerase

Enzyme that adds complementary nucleotides to a growing DNA strand.

Primers

Short DNA sequences that provide a starting point for DNA synthesis.

Ligase

Enzyme that joins DNA fragments on the lagging strand during replication.

Okazaki fragment

Short DNA fragments formed on the lagging strand during discontinuous replication.

Leading strand

DNA strand synthesized continuously in the 5' to 3' direction.

Lagging strand

DNA strand synthesized discontinuously in fragments (Okazaki fragments).

Semi-conservative replication

Each new DNA molecule contains one original and one new strand.

PCR (Polymerase Chain Reaction)

Technique that amplifies a target DNA sequence using primers and a heat-tolerant polymerase.

Template DNA

Original DNA strand used as a pattern for synthesizing a new strand in PCR.

DNA primers

Short, synthetic single-stranded DNA sequences that bind to the ends of the target DNA region in PCR, providing a starting point for DNA polymerase to synthesize new DNA strands.

TAQ polymerase

Heat-tolerant DNA polymerase commonly used in PCR.

Denaturation

PCR step where DNA is heated (92–98°C) to separate strands.

Annealing

PCR step where temperature is lowered (50–65°C) to allow primers to bind.

Extension

PCR step where DNA is extended by TAQ polymerase (70–80°C).

Transcription

Process of copying a DNA sequence into RNA, occurring in the nucleus.

RNA polymerase

Enzyme that synthesizes RNA from a DNA template during transcription.

Promoter

DNA sequence where RNA polymerase binds to initiate transcription.

Exon

Coding regions of a gene that are spliced together to form mature mRNA.

Intron

Non-coding regions of a gene removed during RNA splicing.

RNA splicing

Process of removing introns and joining exons to form mature mRNA.

Mature mRNA

Processed mRNA that exits the nucleus for translation.

Start codon

AUG; signals the start of translation.

Stop codon

Codons that signal termination of translation.

Codon

Three-nucleotide sequence in mRNA that codes for an amino acid.

Anticodon

Three-nucleotide sequence in tRNA that pairs with a codon.

Ribosome

RNA–protein complex where translation occurs to build polypeptides.

Translation

Process of decoding mRNA into a polypeptide chain at the ribosome.

Polypeptide

Chain of amino acids that folds into a protein.

Gene expression

Process by which a gene’s information is used to produce a functional product (protein or RNA).

mRNA

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

tRNA

Transfer RNA; brings specific amino acids to the ribosome during translation.

rRNA

Ribosomal RNA; forms part of the ribosome along with proteins.

Mutation

A heritable change in DNA sequence that can alter a protein or regulation.

Substitution

Single base replacement in DNA; may be missense, nonsense or splice-site.

Insertion

Addition of one or more nucleotides into the DNA sequence.

Deletion

Removal of one or more nucleotides from the DNA sequence.

Frame shift

Insertion or deletion that shifts the reading frame of the genetic code.

Missense

Substitution that changes one amino acid to another.

Nonsense

Substitution that creates a premature stop codon.

Splice-site mutation

Mutation at exon–intron boundaries affecting RNA splicing.

Chromosome mutation

Alterations affecting whole chromosomes (deletion, duplication, inversion, translocation).

Inversion

Chromosome segment flips its orientation.

Translocation

Segment moves to a non-homologous chromosome.

Telomere

Protective chromosome end that prevents unraveling.

Genome

The complete set of genetic material present in an organism or cell.

Non-coding DNA

DNA that does not code for proteins but regulates transcription or yields non-coding RNAs.

Regulatory sequence

DNA regions that regulate gene expression (promoters, enhancers).

Enhancer

DNA element that can increase transcription of a gene.

SNP

Single nucleotide polymorphism; a common genetic variation at a single base pair.

Genomics

Study of the structure, function and mapping of genomes.

Phylogenetics

Study of evolutionary relationships using genetic data.

Molecular clock

Method to estimate evolutionary time based on DNA sequence differences.

Horizontal gene transfer

Gene transfer between organisms in the same generation, common in prokaryotes.

Allopatric speciation

Speciation due to geographic isolation separating populations.

Sympatric speciation

Speciation without geographic isolation, via ecological or behavioral barriers.

Speciation

Formation of new species through isolation, mutation and selection.

Pharmacogenetics

Using genomic information to tailor drug therapies to individuals.

Personal genomics

Sequencing and analyzing an individual’s genome for health or ancestry.

Model organism

A species extensively studied to understand biological processes (e.g., yeast, mice).

Human Genome Project

Large international project that mapped the entire human genome.