Genetic information, variation and relationships between organisms Topic 4

A comprehensive set of vocabulary flashcards covering genetic information, variation, mutations, transcription/translation, diversity, taxonomy, and biodiversity concepts from the notes.

Gene

A base sequence of DNA that codes for the amino acid sequence of a polypeptide or for a functional RNA (including rRNA and tRNA).

Locus

The fixed position of a particular gene on a DNA molecule.

Allele

A different version of the same gene.

Chromosome

Thread-like structure of DNA wrapped around histones (in eukaryotic cells) that carries genes.

Prokaryotic DNA

DNA that is circular, shorter, not wrapped around histones, and not stored in a nucleus.

Eukaryotic DNA

DNA stored as long, linear chromosomes inside the nucleus, wrapped around histones.

Homologous chromosome

A pair of chromosomes that have the same genes and are the same size.

Codon

A sequence of three bases on mRNA that codes for a specific amino acid.

Start codon

Three bases at the start of an mRNA sequence that initiate translation.

Stop codon

Three bases at the end of an mRNA sequence that do not code for an amino acid and cause ribosomes to detach.

Triplet code

A sequence of three DNA bases that codes for a specific amino acid.

Degenerate genetic code

Some amino acids are coded by more than one codon, reducing the impact of substitutions.

Universal genetic code

The same codons code for the same amino acids in nearly all organisms.

Non-overlapping genetic code

Each base is read in one fixed triplet; codons do not share bases.

Frameshift mutation

Insertion or deletion of bases that shifts the reading frame of the gene.

Substitution mutation

One DNA base is swapped for a different one.

Deletion mutation

A base is removed from DNA, often causing a frameshift.

Gene mutation

A change in the DNA sequence that affects a gene.

Chromosome mutation

A change in the number or structure of chromosomes.

Non-disjunction

Chromosomes or chromatids do not separate properly during cell division.

Polyploidy

Having more than two complete sets of chromosomes; common in plants.

Aneuploidy

Abnormal number of individual chromosomes.

Introns

Non-coding sequences within a gene that are removed during processing.

Exons

Coding sequences within a gene that are expressed after splicing.

Splicing

Processing of pre-mRNA where introns are removed and exons joined.

Genome

The complete set of genes in a cell.

Proteome

The full range of proteins that a cell is able to produce.

Anticodon

Three bases on tRNA that are complementary to a codon on mRNA.

mRNA

Single-stranded RNA that carries the genetic code from DNA to the ribosome; codons are read during translation.

tRNA

RNA that carries amino acids to the ribosome and contains an anticodon to pair with codons.

Ribosome

The organelle where translation occurs; catalyses peptide bond formation between amino acids.

Pre-mRNA

In eukaryotes, the initial mRNA transcript that still contains introns and exons.

Spliceosome

The complex that removes introns and joins exons during RNA processing.

Transcription

The process of copying a gene's DNA sequence into mRNA in the nucleus.

Translation

The process where ribosomes synthesize polypeptides using mRNA and tRNA in the cytoplasm.

RNA polymerase

The enzyme that catalyses the synthesis of RNA from a DNA template during transcription.

ATP

Energy source used during translation to form peptide bonds between amino acids.

Haploid (n)

A cell with one copy of each chromosome.

Diploid (2n)

A cell with two copies of each chromosome.

Meiosis

Cell division that produces four genetically different haploid gametes, increasing genetic variation.

Independent segregation

During meiosis, homologous chromosomes separate randomly, creating variety.

Crossing over

Exchange of genetic material between homologous chromosomes, producing new allele combinations.

Gametes

Sex cells (sperm and egg) that carry half the number of chromosomes.

Genetic diversity

The variety of alleles and genes within a population; fuels evolution.

Gene pool

All the genes and alleles present in a population at a given time.

Allele frequency

The proportion of a population that carries a particular allele for a gene.

Evolution

A change in allele frequencies in a population over many generations.

Natural selection

The process by which advantageous traits become more common in a population.

Selection pressure

Environmental factors that affect survival and reproduction, driving natural selection.

Directional selection

Favors one extreme trait; shifts the population mean in one direction.

Stabilising selection

Favors intermediate traits; reduces variation around the mean.

Disruptive selection

Favors extreme traits at both ends of the spectrum; can lead to two peaks in the distribution.

Binomial system

Linnaean naming: genus followed by species (e.g., Homo sapiens).

Courtship behaviour

Species-specific sequences of behaviors used to attract a mate and ensure mating within the same species.

Species

A group of organisms that can breed to produce fertile offspring.

Hierarchy

Smaller groups nested within larger groups with no overlap, reflecting evolutionary relationships.

Phylogenetic classification

Grouping organisms based on evolutionary origins and relationships.

Taxon

Any group in a classification system.

Domain

One of the highest levels in the Linnaean classification: Archaea, Bacteria, Eukarya.

Kingdom

A major taxonomic category used in classification.

Phylum

A primary taxonomic category below kingdom.

Class

A taxonomic category below phylum.

Order

A taxonomic category below class.

Family

A taxonomic category below order.

Genus

A taxonomic category above species; groups species with close relations.

Species richness

The number of different species present in a community.

Index of diversity

A measure of species diversity, relating number of species to individuals per species.

Community

All the species in a particular area at a given time.

Habitat

The physical, biological and environmental space where a species lives.

Biodiversity

The variety of life in an area, including genetic, species, and ecosystem diversity.

Standard deviation

A measure of the spread or variability of a data set around the mean.

Representativeness

How well a sample reflects the population; achieved by large, random samples.

Chloroplast/mitochondrial DNA

DNA similar to prokaryotic DNA: short, circular, not associated with histones.

Transcription differences prokaryotes/eukaryotes

Prokaryotes: transcription yields immediate mRNA with no intron processing; Eukaryotes: pre-mRNA requires splicing to remove introns.