What contains instructions to cells aout how form a heart?

The correct answer is DNA.

DNA, or deoxyribonucleic acid, is a molecule that contains the instructions for an organism's development and characteristics. It is found in the nucleus of cells and is made up of four different types of nucleotides: adenine, cytosine, guanine, and thymine. The sequence of these nucleotides determines the genetic code, which is read by cells to produce proteins. Proteins are the building blocks of cells and tissues, and they carry out a variety of functions, including regulating gene expression, catalyzing chemical reactions, and transporting molecules.

In the case of heart development, the DNA in the cells of the embryo contains the instructions for how to form a heart. These instructions are read by the cells and used to produce proteins that are involved in the development of the heart. For example, some proteins are involved in the formation of the heart chambers, while others are involved in the development of the heart valves. The DNA also contains the instructions for how the heart should function, such as how fast it should beat and how much blood it should pump.