训练：It is possible to make specific complementary DNA's （cDNA's）that can serve as molecular probes to seek out the messenger RNA's （mRNA's）of the peptide hormones. If brain cells are making the hormones，the cells will contain these Mrna'S. If the products the brain cells make resemble the hormones but are not identical to them，then the cDNA's should still bind to　　these mRNA's，but should not bind as tightly as they would to mRNA's for the true hormones.

答案见下期