Glossary

• Chromatids = one half of a duplicated chromosome
• Chromosome mutation = changes in the number or structure of chromosomes
• Crossing over = cellular process that happens during meiosis when chromosomes of the same type are lined up
• Diploid = cell containing two copies of each chromosome
• Gamete = reproductive cell of an animal or plant
• Gene mutation = alteration in the sequence of DNA bases in a gene
• Haploid = cell that contains a single set of chromosomes
• Non-disjunction = when chromosomes do not separate properly during meiosis
• Polyploidy = having more than 2 sets of chromosomes
• Recombination = the exchange of genetic material between chromosomes
• Species = a group of organisms that can breed to produce fertile offspring
• Genetic diversity = number of different alleles of genes in a population
• Allele frequency = relative frequency of an allele at a particular locus in a population
• Gene pool = set of all genes present in any population usually of a particular species
• Directional selection = type of natural selection in which one extreme phenotype is favoured
• Stabilising selection = type of natural selection in which the population mean stabilises on a non-extreme trait value
• Normal distribution curve = describes a symmetrical plot of data around its mean value
• Polygenes = gene whose individual effect on a phenotype is too small to be observed