To be able to write your own cover letter, read the generic letter of recommendation samples given below. The letter of recommendation is used in many fields, especially in the field of education.
This supports the idea that in embryos from wild-type mothers, dpp H~- mutations cause the transformation of dorsal into ven-tral epidermis. If tissue determined to become dorsal epidermis dies in the dpp rim-null embryos, then one should not see ventral or lateral tissue formed in the double-mutant combination.
The trp operon is regulated through negative control only. When tryptophan is present, the operon genes are not transcribed. The lac operon is regulated through both negative control and positive control. Negative control: When lactose is absent, the repressor protein is active, and transcription is turned off.