What are mutations?

Mutations refer specifically to variations in the nucleotide sequence of a gene. These changes can occur in various ways, such as substitutions, insertions, or deletions of nucleotides in the DNA sequence. Such alterations can affect how a gene is expressed or how the corresponding protein is produced, potentially leading to changes in an organism's traits or its susceptibility to certain diseases, including cancer.

Understanding mutations is crucial in the context of chemotherapy and immunotherapy, as mutations can influence how cancer cells respond to treatment. For instance, certain mutations might lead to resistance against specific drugs, making it imperative to identify and understand these genetic changes in targeted therapies.

The other options relate to different cellular or molecular processes but do not accurately define what a mutation is. For example, alterations in protein structure, changes in organelle structure, and transformations in protein synthesis are important biological phenomena but do not capture the specific definition of mutations, which is centered around the genetic sequence itself.