Question

All of the following are sexual sources of genetic variation except

• A. Crossing-over
• B. Mutation
• C. Production of offspring from two parents
• D. Random fertilization

Answer 1

Answer: (B)

Mutation

• A mutation is the permanent alteration of the nucleotide sequence of the genome of an organism, virus, or extrachromosomal DNA or other genetic elements.
• Mutations result from errors during DNA replication (especially during meiosis) or other types of damage to DNA (such as may be caused by exposure to radiation or carcinogens), which then may undergo error-prone repair (especially microhomology-mediated end joining), or cause an error during other forms of repair.
• Mutations may or may not produce discernible changes in the observable characteristics (phenotype) of an organism.
• Mutations play a part in both normal and abnormal biological processes including evolution, cancer, and the development of the immune system, including junctional diversity.
  

So the correct option is 'mutation'.