1 Insertion â when a base is added to the sequence. 2  Deletion â when a base is deleted from the sequence.  Copy number variation (CNV) is a type of mutation where large chunks of DNA are inserted, repeated or lost. These regions of DNA can be between 10,000 and 5,000,000 bases long.
Wind deposition can result in dunes and loess deposits.
The dunes, with their various forms, raise many questions about the dynamics of their formation. Sahara's most famous features are the ergs, or sand dune seas, most of it is really hamada, or rocky plateau. Water. The Sahara has only two permanent rivers and a handful of lakes, but it has substantial underground reservoirs, or aquifers.