Virtual karyotypes have dramatically higher resolution than conventional cytogenetics. Trisomy 8, chromosome 7 abnormalities and complex karyotypes comprise a high risk group. The banded karyotypes of 850 mammalian species were summarized in the "Atlas of Mammalian Chromosomes". Therefore, virtual karyotypes cannot detect balanced translocations and inversions. This is approximately 1000-fold greater resolution than karyotypes obtained from conventional cytogenetics. Normal karyotypes or the single loss of the Y chromosome have low risk prognoses. Different karyotypes may have differing rates of cardiovascular malformations. The preparation and study of karyotypes is part of cytogenetics. The preparation and study of karyotypes is part of cytology and, more specifically, cytogenetics. Ensembl Genomes allows comparing and visualising user data while browsing karyotypes and genes. The number of autosomes in all karyotypes was 58. The main methods used for creating virtual karyotypes are array-comparative genomic hybridization and SNP arrays. Unlike euploidy, aneuploid karyotypes will not be a multiple of the haploid number. Researchers have also noted how stable these aberrant karyotypes can be. Microchromosomes are absent from the karyotypes of mammals, crocodilians, and frogs.