The process in which a gene from one organism is inserted into the DNA of another organism is called genetic engineering or recombinant DNA technology. It is done to transfer the desirable trait of one organism to another to produce a better organism.
In the text it says “Most macromolecules are made from single subunits, or building blocks, called monomers. The monomers combine with each other using covalent bonds to form larger molecules known as polymers. In doing so, monomers release water molecules as byproducts. ... In the process, a water molecule is formed.” I hope this helped
In DNA, the "rungs" between the two strands of DNA are formed from the nitrogenous bases adenine, thymine, guanine and cytosine