Why are the Officials searching Cassia's house after Grandfather is gone?

Something is wrong at Cassia's house. The neighborhood is shut down, and Officials are searching her home. She is worried that they have discovered that she has the writing, and she hides it once again. She isn't the problem, though. The Officials are there because her father never turned in Grandfather's tissue samples. He lost them. This horrifies Cassia because it means Grandfather is truly gone. They will never be able to bring him back with the advances of science. Her mother defends her father because she loves him. Bram tries to offer the watch Grandfather gave him as a sample for the Officials, but they say it isn't enough and won't work.