The Three Steps to Microfacturing

Now that you understand the basic rules under which cells operate, let’s look at how DNA can be ‘recognized,’ ‘read’ and ‘executed’ by the cell. During the hands-on exercise in this chapter, you genetically engineered your cells with a DNA plasmid. Immediately after you put the DNA into the cells, they began what we call the Three Steps to Microfacturing. Microfacturing is like manufacturing, except it happens at the micro-scale or smaller. This is what scientists are referring to when they talk about genetic expression.

We’ve seen that the order of nucleotides in a DNA sequence make up the ‘blueprints’ for the cell. The Three Steps to Microfacturing, describes three distinct and separate processes that cells use to recognize and read DNA sequences, ultimately decoding it to make cellular products that have a function (Figure 4-18).

Figure 4-18. The Three Steps to Microfacturing includes DNA being transcribed into RNA, and RNA being translated into proteins. Becoming a Genetic Engineering Hero means knowing how all of these steps work so that you can control what the cell makes, when the cell makes it, and how much it makes!

Step 1 - Transcription: DNA is a stable chemical molecule with unique sequences. Some regions of DNA have a specific sequence that can be recognized by cellular machinery. As you just learned, this recognition happens when a chemical bond that is strong enough exists between the cellular machinery and the shape and physical characteristics of the DNA segment. In the first step of the Three Steps to Microfacturing, DNA becomes bound to and is ‘read’ by cellular machinery called RNA polymerase.

RNA polymerase travels along the DNA reading it and simultaneously transcribing a similar looking, but different nucleic acid string called ribonucleic acid (RNA). Just like how a language translator can listen to Spanish and translate to English in real-time, RNA polymerase reads DNA and simultaneously creates the appropriate RNA molecule. We are going to cover transcription and RNA in depth in this chapter.

Step 2 - Translation: As you will learn in the coming sections, RNA is a less stable chemical molecule than DNA, but both molecules share many similar characteristics. In step two of the Three Steps to Microfacturing, another kind of protein machinery called a ribosome recognizes a region of the RNA through chemical bonding, along with help from a distinct type of RNA called transfer RNA (tRNA).

The ribosome and tRNA read the RNA, simultaneously translating the RNA sequence into strings of amino acids called proteins. As you learned in Chapter 3, proteins make up the vast majority of cellular machinery. For example, in this chapter’s hands-on activity, the color pigment produced by your cells was likely a protein. The antibiotic resistance was also due to a protein. Translation, tRNA and protein creations will be covered in Chapter 5.

Step 3 - Enzymatic Processing: The third step of the Three steps to Microfacturing is Enzymatic Processing. This includes how protein enzymes cause the chemical reactions that make life happen. We will cover it in Chapter 6.

Now, let’s have a deeper look at Step 1, transcription. To do so, we will first learn about a very important nucleic acid, ribonucleic acid, or RNA.