Final answer:
The type of damage caused by an improperly paired base in DNA is known as a mismatch, and it is repaired by the mismatch repair system.
Step-by-step explanation:
The name of the type of damage caused by an improperly paired base in the DNA is known as a mismatch. This occurs during DNA replication when the wrong DNA base is stitched into place in a newly forming DNA strand, or a DNA base is skipped or mistakenly inserted. The mismatch repair mechanism is responsible for detecting and repairing these errors post-replication, helping to maintain the integrity of the genetic code. Other forms of DNA damage include double-strand breaks, depurination, and the formation of thymine dimers, each with their respective repair mechanisms such as homologous recombination, base excision repair, and nucleotide excision repair.