The -DNA plate and -DNA/+amp were control plates, no colonies were supposed to grow on these plates because of the -DNA, which occurred. The +DNA/+amp and +DNA/+amp/+IPTG plate were the experiment plates since it had +DNA instead of -DNA. Additionally, the cells on these two plates would transform and the plate would form colonies since they were the experiment plates.

The purpose of incubating the cells in ice, then 42oC ice water, then back to ice was because to transform the cells and take in the DNA, the DNA must be added to the cells in the presence of specific chemicals like calcium, magnesium chloride, etc, and to heat shock them by moving them quickly between widely different temperatures (ice then 42oC then ice). This is because it