Sigh... very confusing to a beginner. So we need to be buying "heirloom" only ? and we should be safe from anything thats been altered.
Cross pollination isnt a "bad" thing right ? Sounds like it could be. Its still mixing the genetics isnt it ?
1) If you do not want any seed that has been altered, then "Heirloom" would be your choice.
2) Cross pollination isn't necessarily bad. It happens naturally. "Cross pollination is a natural method in which transfer of pollen takes place from an anther of a flower of one plant to a stigma of a flower of another plant of the same species. "
Lots of gardeners experiment with cross pollination especially in tomatoes. For myself, I find many hybrid varieties superior in certain characteristics than "heirloom" varieties. Particularly in corn and tomatoes, traits that are highly desirable can be assured in certain hybrids.
If you save seed for future use, then don't save seed from hybrids but only from heirlooms. The so called F1, F2 offspring from hybrid seed are usually not desirable, nor true to the first cross.