What does it mean to have three parents?

I commented on this briefly in a blog post some time ago, but this topic has seen a resurgence in the media lately. This past week, the British House of Commons voted to allow for the creation of a baby made with the genetic material of three people, so called "three-person babies". Not surprisingly, this has some people up in arms over the ethics of such a procedure, as well as its implications for the future of genetic modification. I even saw someone call it "letting the gene out of the bottle". Clever! In true Kitchen Table Science fashion, I'm going to give you a brief overview of what this technology is and what is it meant to correct. Just the facts ma'am, just the facts!

1. The Mitochondria

You may remember from high school that the mitochondria is the powerhouse of the cell, responsible for the majority of energy generation for your body. You may also remember that it, in fact, has its own genetic material independent of the rest of your genome. The reasoning behind this is theoretical and may be discussed in a future post, but know that the DNA present in your mitochondria comprises less than a tenth of a percent of your overall genetic code. Its 37 (versus the remaining 20-25,000 genes in your genome) genes do not influence anything related to appearance, intelligence, or anything along those lines.

2. Mitochondrial disease

As with all genes, your mitochondrial DNA is susceptible to mutations. These mutations can cause a family of disease known as mitochondrial diseases. Symptoms of these diseases vary wildly and include poor growth, muscle weakness, and poor coordination. Since your mitochondria process DNA separately from the rest of the cell, you can theoretically correct for mitochondrial disease by replacing the damaged organelle with a healthy one in the embryo. The healthy mitochondria would continue to be passed down to the cells in the developing embryo, ensuring that all cells in the fully formed human will have good mitochondria. Below is a great graphic from the Human Fertilization and Embryology Authority on how this works:

Figures 1 and 2: Proposed methods for correcting mitochondrial genetic abnormalities

So is this safe and/or ethical? Technically speaking, yes, the resulting child will have the genetic material of three different people. Calling the donor of the mitochondria a "parent" though is a pretty big stretch, considering how little of the DNA contributed will actually affect the rest of the body. It is impossible to predict whether or not something will be completely safe when it comes to procedures like this - only time will be able to tell us that.

I'll leave it for you to decide whether or not society should proceed with this technology. My opinion? This presents an exciting new way to correct for some devastating diseases, and am I certainly looking forward to seeing how this technique evolves in the coming months!