Perhaps subject an adult to the modification first, on the condition that they're happy to accept risk - and then use that as one's source of reference.

As A Biologist I believe this should be allowed. As it has promise to greatly enable us to eradicate potential DNA-based birth defects in the future.

The UK Government earlier this year also began doing it. And I believe the US will apply next year.

On February 3, 2015, the UK voted to authorize mitochondrial DNA modification. This new law has been dubbed the “three-person embryo” and “three-person babies” law.

(It isThe mitochondria in our cells carries important DNA in addition to the DNA found in the nucleus of cells. Unfortunately, some mothers carry potentially fatal or incurable diseases within their mitochondrial DNA that are passed on to their children.)

You have to be aware that, Throughout the world, a child is born every 30 minutes who will develop a mitochondrial disease before age 10. A child who is born with unhealthy mitochondrial DNA can show many symptoms, such as seizures, diabetes, muscle weakness or loss of muscle coordination, or neurological problems.

Most people with such a disease do not survive past their teen years. The “three-person embryo” law will allow doctors to replace the nucleus from a healthy donor egg with the nucleus from an egg with mitochondrial DNA mutations, which can then be fertilized, thereby creating an embryo from three different people (or replace the nucleus from the donor egg with the parents’ nuclear material from a fertilized egg).

This advanced scientific process, which used to be a fictional concept, has been a reality for several years, but has only now been legalized. The controversial and notable decision has sparked hope for mothers who carry mitochondrial diseases. However, it has also fueled considerable debate. Some worry that legalizing mitochondrial DNA alteration will open the door to people selectively modifying the physical attributes of an embryo contained in the nuclear DNA.

There are strong opinions on both sides of this issue. People who support genetically modifying (changing) mitochondrial DNA are interested in eliminating unhealthy or fatal diseases in newborns, which could prolong life for dozens of years. The ability to replace mitochondrial DNA helps alleviate the worries of mothers who have mitochondrial DNA mutations that would be passed on to their children.

Too, There is also a biological imperative that points towards modifying DNA. People are driven to keep the human race alive. Humans have, for thousands of years, been developing technology and medicine which has influenced human heredity. DNA modification is simply the next step in creating a more stable species.

BUT.......On the other hand, people who disapprove of mitochondrial modification argue that it could potentially lead into the boundaries of nuclear DNA modification. Not only does nuclear DNA modification have the potential to change phenotypic, or physical, characteristics, but it may also open the doors to designing certain personalities and enhancing specific abilities of the embryo, such as a child’s future athleticism.

This method of artificially sculpting near-perfect humans raises some ethical concerns. It resembles the concept of eugenics, which is the idea of selectively breeding a certain type or race of people. In addition, some see the genetic manipulation as an increase in the gap between the rich and poor.

And of course Wealthier families will have a privilege of changing the DNA of their embryos, while people with lower incomes will not. Finally, Thomas Malthus, an English scholar of the 18th century, dictated that diseases and genetic variability in a population is essential for a stable community.

I can say that I myself believe that If it becomes the norm to manipulate mitochondrial DNA, and eventually nuclear DNA, to reduce genetically-caused diseases, human genetic variation may substantially decline and cause the human population to crash in the long term.

I don't think we should allow it.

I can see the point of reducing genetic disease, and controlling more factors that used to be random, but, for me it is clearly unethical.

I think it is for several reason: first of all, you remove what make people unique, maybe not now, but the evolution of this technique might allow more standardization in a few years/ decades.

On a second point, I am against all kind of DNA manipulation, as you are just playing with what is bearing live in our bodies, without knowing the consequences of your acts.

The last main point is that we must leave the natural selection occur, and stop overpopulation, instead of trying to save a few people from natural death.