The option that would lead to increased genetic variation in offspring is:
- A DNA replication error in a gamete of an individual during meiosis.
This is because DNA replication errors can introduce mutations, which can result in new alleles. While crossing over and independent assortment are important for generating variation during meiosis, the option specifically mentions a mechanism that directly contributes to new genetic variation through potentially significant changes in the DNA sequence. Note that crossing over occurs in meiosis, not mitosis, so the statement about crossing over during mitosis is incorrect in this context.