Chromosomal. Chromosomes are the packaging for the genes. Genes are made up of dna. Chromosomal abnormalities are extra chromosomes, deletions, duplications, or translocations of large chunks of dna.
Generally speaking. Chromosomal disorders are disorders of entire chromosomes. Remember, we have 23 pairs of chromosomes for 46 total. Downs syndrome is a 3rd copy of chromosome #21 in its entirety. A single gene disorder would be disorders like sickle cell, cystic fibrosis or thalessemia. In which the chromosome looks and is normal, but the gene at that site on the specific chromosome is specific to the disease.