A sudden change in a gene, such as a nucleotide shifting its position, is known as a:

1. Genes are usually transmitted to the next generation unchanged. 2. Sometimes a sudden change occurs in a gene, for example a nucleotide changing its position. 3. Such a minor sudden change is called a mutation. 4. Translation and transcription are normal synthesis steps, so they are ruled out. _Source: Balbharati (Maharashtra Board) Class 10 Science & Technology Part 2, Ch 1 "Heredity and Evolution", p.11_