Can you explain this better to me?

It sounds like the lymphocyte is just looking at one part of the gene, which gives it a specific polypeptide, then it looks at different gene and that gives a different specific polypeptide. So the lymphocyte is taking different parts of the gene,coding them, then combining them to produce different antibodies. (so having parents with very different dna would be beneficial because the lymphocyte has a bigger selection to choose from when making its antibodies)