Biology External Revision Guide

A set of vocabulary practice flashcards derived from the Biology External Revision Guide covering DNA structure, cell division, gene expression, genetics, biotechnology, evolution, speciation, and biodiversity sampling methods.

DNA

A double-helix molecule that stores genetic information.

Nucleotides

Building blocks of DNA made of a sugar, phosphate group and nitrogenous base.

Genes

Sections of DNA that contain instructions used by cells.

Chromosomes

Structures that package DNA; DNA wraps around histone proteins to become compact.

Endosymbiotic theory

The theory that mitochondria and chloroplasts evolved from engulfed bacteria, supported by evidence such as double membranes and independent circular DNA.

Helicase

An enzyme that breaks hydrogen bonds and separates DNA strands during replication.

Primase

An enzyme that adds RNA primers to provide a starting point during DNA replication.

DNA polymerase

An enzyme that adds complementary nucleotides to build new DNA.

Ligase

An enzyme that joins fragments on the lagging strand during DNA replication.

Lagging strand

A DNA strand built in Okazaki fragments because DNA polymerase works in one direction.

Mitosis

A cell division process resulting in one division that produces two genetically identical diploid body cells.

Meiosis

A cell division process resulting in two divisions that produce four genetically different haploid gametes.

Homologous chromosomes

Similar chromosomes with the same genes at the same loci, although alleles may differ.

Spermatogenesis

A process occurring in the testes that produces four haploid sperm cells from one primary spermatocyte.

Oogenesis

A process occurring in the ovaries that produces one mature egg plus smaller polar bodies.

Genome

The complete genetic material of an organism.

Coding DNA

DNA sequences used to make proteins.

Non-coding DNA

DNA regions including regulatory regions, introns, telomeres and sequences involved in RNA production.

Exons

Coding sequences retained in mature mRNA.

Introns

Non-coding sequences removed during RNA splicing.

Transcription

The process where DNA information is copied into mRNA in the nucleus.

Translation

The process where mRNA is read at ribosomes in codons to assemble amino acids into a polypeptide/protein.

mRNA

RNA that carries genetic information from DNA to ribosomes.

tRNA

RNA that carries specific amino acids and has anticodons that pair with mRNA codons.

rRNA

RNA that forms part of ribosomes and assists protein synthesis.

HOX genes

Transcription factor genes involved in body patterning during development.

SRY gene

A gene on the Y chromosome involved in sex determination.

Mutation

A change in a DNA sequence or a broader chromosomal change.

Frameshift mutations

Insertions or deletions not divisible by three that can alter the reading frame and affect downstream codons.

Mutagens

Environmental agents that can damage DNA.

Non-disjunction

Failure of chromosomes or chromatids to separate correctly, potentially producing cells with missing or extra chromosomes.

Recombinant DNA

DNA from different sources combined using laboratory techniques.

PCR

Polymerase chain reaction; amplifies small DNA samples into millions of copies through denaturation, annealing, and extension cycles.

Gel electrophoresis

Technique that separates DNA fragments by size as negatively charged DNA moves toward the positive electrode.

Microevolution

Small-scale changes in allele frequencies within populations.

Macroevolution

Large-scale evolutionary change over long periods, including diversification and formation of new species.

Gene flow

Movement of genetic variation between populations.

Genetic drift

Random changes in allele frequencies that can cause alleles to be lost.

Gene pool

The total genetic variation available within a population.

Directional selection

Selection pressure where one extreme phenotype is favoured, shifting the population toward that extreme.

Stabilising selection

Selection pressure where intermediate phenotypes are favoured, reducing variation around the average.

Disruptive selection

Selection pressure where both extreme phenotypes are favoured over intermediate phenotypes.

Adaptive radiation

An evolutionary pattern where one ancestral species rapidly diversifies into many species adapted to different niches.

Divergent evolution

An evolutionary pattern where related species from a common ancestor become increasingly different.

Convergent evolution

An evolutionary pattern where unrelated species independently evolve similar traits because of similar selection pressures.

Parallel evolution

An evolutionary pattern where closely related species independently evolve similar traits under similar pressures.

Coevolution

An evolutionary pattern where two or more closely interacting species influence each other's evolution.

Phylogeny

The evolutionary history and relationships among organisms.

Comparative genomics

The comparison of DNA and genetic material, where greater similarity generally indicates a closer evolutionary relationship.

Speciation

The formation of new, distinct species through accumulated evolutionary differences.

Allopatric speciation

Speciation where geographic isolation prevents gene flow between populations.

Sympatric speciation

Speciation where new species arise in the same geographic area through reproductive isolation or ecological differences.

Parapatric speciation

Speciation where geographically adjacent populations diverge into distinct species.

Cladistics

A system that classifies organisms according to evolutionary relationships and common ancestry.

Binomial nomenclature

A classification system where scientific names consist of Genus + species.

R-selected species

Species that generally produce many offspring, provide less parental care and tend to have shorter lifespans.

K-selected species

Species that generally produce fewer offspring, provide greater parental care and tend to have longer lifespans.

Belt transect

A biodiversity sampling method that measures abundance and distribution across an environmental gradient or strata.

Line transect

A biodiversity sampling method useful for measuring distribution along a gradient but not detailed abundance.

Random quadrats

A biodiversity sampling method useful for measuring abundance, but which may not show changes across different strata.