Idiochromosomes are chromosomes that are similar in appearance to other chromosomes but differ in some way, such as size or shape. There are a few synonyms for the term idiochromosome, including identity chromosome, unique chromosome, and individual chromosome. Other related terms include homologous chromosomes, which are similar in size and shape and carry genes for the same traits, and heterozygous chromosomes, which have different alleles for a given gene. The study of idiochromosomes is an important aspect of genetics research and can provide insight into the mechanism of evolution and the genetic basis of complex traits.