Nonsense Mutation: A mutation in a DNA sequence that results in a premature stop codon, or a nonsense codon in the transcribed mRNA, and possibly a truncated, and often nonfunctional protein product.
Missense Mutation: A type of mutation where one nucleotide is replaced by another. The change can result in coding for a different amino acid.
Chromosomal Deletion: This is when an entire section of chromosome is deleted during DNA replication.