The following is a script of “Breeding out Disease” which aired on Oct. 26, 2014. Norah O’Donnell is the correspondent. Tanya Simon, producer.

There are few fields of medicine that are having a bigger impact on how we treat disease than genetics. The science of genetics has gotten so sophisticated so quickly that it can be used to not only treat serious diseases but prevent thousands of them well before pregnancy even begins. Diseases that have stalked families for generations - like breast cancer - are being literally stopped in their tracks. Scientists can do that by creating and testing embryos in a lab, then implanting into a mother’s womb only the ones which appear healthy. While the whole field is loaded with controversy, those who are worried about passing on defective and potentially dangerous genes see the opportunity to breed out disease.

Norah O’Donnell: Did you ever envision that you would have the capability you have today?

Dr. Mark Hughes: No, but that’s the fun of science. It’s constantly surprising you.

[Dr. Mark Hughes: Wow. Look at that.]

“If it’s a mutation in a particular gene that causes early onset, we can test for it...”

Dr. Mark Hughes is one of the scientists leading the way in a rapidly growing field known as reproductive genetics. He pioneered a technique called preimplantation genetic diagnosis, or PGD, an embryo screening procedure that can identify deadly gene mutations - and alter a child’s genetic destiny.

[Dr. Mark Hughes: This one’s got a minus two.]

Dr. Mark Hughes: We all throw genetic dice when we have children. But when you know the dice are loaded and that there’s a really reasonable chance that your baby will have an incurable, dreadful condition, you’re looking for an alternative.

Dr. Hughes helped develop PGD two decades ago to screen embryos for one disease: cystic fibrosis. Today, because of advances in the mapping of the human genome, he says it can be used to root out virtually any disease caused by a single defective gene.

Norah O’Donnell: Let me do a rapid fire yes or no. Can you use PGD for Tay-Sachs?

Dr. Mark Hughes: Yes.

Norah O’Donnell: Muscular dystrophy?

Dr. Mark Hughes: Yes.

Norah O’Donnell: Sickle-cell anemia?

Dr. Mark Hughes: Yes.

Norah O’Donnell: Hemophilia?

Dr. Mark Hughes: Yes.

Norah O’Donnell: Huntington’s disease?

Dr. Mark Hughes: It’s one of the most common disorders we test for, yes.

Norah O’Donnell: Alzheimer’s disease?

Dr. Mark Hughes: If it’s a mutation in a particular gene that causes early onset, we can test for it, yes.

Norah O’Donnell: So you can test for Alzheimer’s.

Dr. Mark Hughes: This is a small subset of a particular kind of Alzheimer’s that attacks very early in life.

Norah O’Donnell: Colon cancer?

Dr. Mark Hughes: If we know which of the colon cancer genes, yes.

Norah O’Donnell: Breast cancer?

Dr. Mark Hughes: We do it regularly.

Dr. Hughes’ lab is one of a handful in the country that provides this genetic testing, which is why 3,000 couples turn to him each year. Among them, Matt and Melinda, who asked that we not use their last name. If they hadn’t done the embryo screening procedure, their four-year-old son Mason and his baby sister, Marian, might very well have been born with a genetic mutation that increases the risk of breast, ovarian, prostate, and pancreatic cancer. It wasn’t until Melinda herself was diagnosed with an aggressive form of breast cancer seven years ago that she found out she carried that gene mutation known as BRCA1.

“It’s a lifetime of having to worry about it. And I just didn’t want my kids to have to do that.”

Norah O’Donnell: Did you know what BRCA1 was?

Melinda: Not a clue.

But as it turned out, it had haunted her family for generations. At age 29, facing chemotherapy and a double mastectomy, Melinda was afraid that if she had children one day, they would also be cursed with that potentially deadly mutation.

Norah O’Donnell: What did doctors tell you about the risk of passing on this BRCA mutation?

Melinda: Fifty percent. So flip a coin.

Norah O’Donnell: And I bet that weighed on you even heavier.

Melinda: Yes. It’s a lifetime of having to worry about it. And I just didn’t want my kids to have to do that.

The best way to ensure that was to do embryo screening for the BRCA1 gene mutation, which Dr. Hughes says is among the fastest-growing parts of his business.

Dr. Mark Hughes: This takes the risk. For example, in breast cancer, it takes the risk if you have this mutation from 50/50 of passing it to the next generation down to less than one percent.

But the screening isn’t easy. All couples, even fertile ones, must first go through in-vitro fertilization, the process in which a man’s sperm is injected into a woman’s eggs under a microscope to create embryos. Then, five days later, a tiny tube just one twentieth the diameter of a human hair is used to extract from each embryo one single cell to be genetically tested for disease.

Norah O’Donnell: It’s just one cell?

Dr. Mark Hughes: Yes.

Norah O’Donnell: You can tell that much from one cell?

Dr. Mark Hughes: You can tell an awful lot in one cell.

“Was it right? Was it the right thing to do? Is it playing God? Is it ethical?”

That cell is packed up at fertility clinics across the country and shipped overnight in ordinary looking boxes like these to screening labs. We followed the process at Dr. Hughes lab, called Genesis Genetics just outside Detroit, where a team of scientists took over.

Norah O’Donnell: So what do you do with that one cell when it arrives here?

Dr. Mark Hughes: Well we’re busy. We have to break the cell open; they have to pull out this enormous encyclopedia of genetic information.

He’s talking about the cell’s DNA, our genetic code that scientists represent with four letters - A, C, T and G. For a gene to work properly, the letters have to be strung together in the right order. If they’re not, that could spell trouble. It’s Dr. Hughes’ job to find the mutation - or “typo” - in a gene that could cause disease.

Dr. Mark Hughes: So you have to find that typo in effectively six billion letters.

Norah O’Donnell: A typo in six billion letters?

Dr. Mark Hughes: Yeah.

Norah O’Donnell: So how do you do that?

Dr. Mark Hughes: Technology is amazing.

Dr. Hughes used the technology to screen Matt and Melinda’s embryos in 2010 - ruling out the ones that carried the BRCA1 mutation, which would have given their children a reasonable chance of getting breast or other cancers.

Norah O’Donnell: About how many of them tested positive for the BRCA1 gene?

Dr. Mark Hughes: About half and indeed, if you look at her embryos, here is an affected, an affected, an affected, an affected. That’s four. It’s about half. It is just what you’d expect.

It’s just what you’d expect in nature. But with the powerful intervention of science, embryos that carry a harmful mutation are often discarded, which is one reason the decision to go ahead with the screening was a difficult one for Matt and Melinda.

Melinda: We prayed a lot about it. It’s a hard decision to make.

Norah O’Donnell: What did you struggle with?

Melinda: Was it right? Was it the right thing to do? Is it playing God? Is it ethical? And the more we learned about it and got comfortable with the idea, it was like, “Yes, absolutely.”

Norah O’Donnell: You have said, “The breast cancer stops with me.”

Melinda: Yes. It’s not just my children. It’s their children and my grandchildren and great grandchildren. Forever and all for time, in my bloodline, yeah.

The entire process cost them around $16,000 - a small price to pay, Melinda says, for her children’s health.

But Anne Morriss didn’t get to change the odds for her child. By the time she learned she carried a dangerous mutation, she had already passed it on to her son, who’s now seven. At birth, Alec seemed the picture of health, but then came an unexpected call from a doctor.

Anne Morriss: He started by saying, “Can you please go check and make sure that your child is still alive and then come back and we can continue this discussion.”

Norah O’Donnell: So a doctor calls you and says, “I need to tell you something but can you go check that your son is still alive.”

Anne Morriss: That’s how the conversation started.

Norah O’Donnell: What was your reaction?

Anne Morriss: You know, your heart just falls out of you.

A newborn screening test revealed Alec had a rare and sometimes fatal metabolic disorder called MCAD deficiency; he had to be fed every few hours just to stay alive.

Unlike breast cancer, MCAD deficiency is a recessive disorder, meaning a child must inherit a copy of the faulty gene from both parents. Anne Morriss had used an anonymous sperm donor to conceive, but in an incredible case of bad luck, he just happened to carry the same mutation she did.

Anne Morriss: Every human being walking the planet is a carrier for a rare disease. But what matters is who we choose to partner with reproductively. Like, that’s where the risk shows up.

Now she wants to reduce the risk of a bad genetic match for others - well before they start the reproductive process. She just started a company called GenePeeks with Lee Silver, a Princeton University professor who’s also a molecular biologist -- though his latest idea doesn’t take place in a lab. It’s entirely virtual.

Lee Silver: We are creating digital babies.

Norah O’Donnell: Digital babies?

Lee Silver: Yes.

Norah O’Donnell: So you’re simulating the process of reproduction, but on a computer.

Lee Silver: Exactly.

Silver says all it takes is a saliva sample to obtain DNA. He then combines the genetic information from both prospective parents in a computer to make a thousand digital babies.

Norah O’Donnell: this is a digital baby.

Lee Silver: This is a digital baby.

It contains virtual DNA - which like real DNA, is represented by those same four letters - A, C, T and G.

Lee Silver: This baby has a mutation.

He says that by analyzing the DNA in all those digital babies, he is able to calculate the risk of two people conceiving a child with any one of 500 severe recessive pediatric disorders.

For now, GenePeeks is available for $2,000 to clients using sperm banks and egg donors to conceive, though its founders say the goal is to expand it to all couples who want to have a baby.

Norah O’Donnell: You think everyone who’s going to have a baby should go and have a digital baby first?

Lee Silver: I see a future in which people will not use sex to reproduce. That’s a very dangerous thing to do.

That may sound far-fetched, but the way Lee Silver sees it, there will come a time when couples will no longer want to conceive naturally because it’s too risky.

Lee Silver: It’s safer to have a baby with this pre-knowledge, this genetic information that might help them avoid disease.

“I think it’s going to be used by society in the 21st century, just like we used antibiotics and other advances in the 20th century...”

But with the promise of this technology also comes the fear that some parents would want to use it to select genetic traits in their children that have nothing to do with disease - a debate Lee Silver himself stoked when he wrote the patent for GenePeeks.

Norah O’Donnell: We read your patent and it says your technology could be used to assess whether a child could have other traits, like eye color, hair color, social intelligence, even whether a child will have a widow’s peak? If your company is so focused on preventing disease, why would you include those traits?

Lee Silver: The purpose of the list of traits is simply to demonstrate that our technology can be used to study anything that’s genetically influenced. That doesn’t mean we’re going to actually do that.

Norah O’Donnell: OK. But you’re running a company? That could be big business?

Lee Silver: We are the ones who invented this technology and we’re going to use it to study pediatric disease. At the moment, we will make sure the technology is used only for that purpose.

And at the moment, you’ll have to take his word for it because there are no real rules in this country limiting what this kind of technology can be used to screen for, leaving those decisions up to scientists like Lee Silver and Mark Hughes.

Norah O’Donnell: So we should trust you to set the boundaries?

Dr. Mark Hughes: If I’m setting a boundary saying, “I’m not willing to do that,” that’s no different from any other field of medicine. So sure.

Norah O’Donnell: But do you wrestle with this at all? I mean, who is the gatekeeper?

Dr. Mark Hughes: That’s the question. Should it be some group sitting around a mahogany table or should it be all left up to the patient? If it would get to the point where it was like cosmetic surgery, that would be downright awful. But I’d think those are all straw men arguments. And people asked me these very questions that you’re asking me right now, 25 years ago. And it hasn’t happened.

That’s in part because researchers still only fully understand traits and diseases caused by a single flawed gene. There’s a lot left to learn about the interaction of multiple genes. But when that happens, Mark Hughes and Lee Silver believe their technologies will be able to screen for a host of genetically complex diseases that they say could include schizophrenia, and some types of diabetes and heart disease.

Lee Silver: I think it’s going to be used by society in the 21st century, just like we used antibiotics and other advances in the 20th century, to drastically reduce the risk of infectious disease. We’re going to be able to drastically reduce the risk of genetic disease.

Norah O’Donnell: You’re comparing this ability with reproductive genetics to antibiotics and vaccinations?

Lee Silver: I am. And in some ways, this is more powerful.

Earlier this month, because of how quickly the industry is growing, the FDA proposed guidelines to review certain genetic testing to ensure the technology used in the diagnosis of serious diseases is accurate and safe.