It’s like the stuff of science fiction.

Boot up your computer. Choose the traits that you want — maybe brown eyes or musical ability or resistance to cancer.

And press start.

A machine in your lab then starts to piece together the chemical building blocks of DNA.

In the end, you will have the entire genetic code — or genome — needed to create a human designed to your exact specifications.

This scenario is not possible now, but a group of scientists hope to make it a reality — or at least technically feasible — within 10 years.

Some critics are concerned this technology could lead to designer babies or genetic superhumans.

But the group of researchers says their plans are less fantastic, although just as game changing for the field of genetic engineering.

Read More: What Is Genomics? »

Writing the Human Genome More Cheaply

The human genome is made up of four chemical subunits — nucleotides — that form the genetic code of our DNA and genes.

The specific order of the nucleotides determines how our bodies look and function — although environmental conditions also have an effect.

Variations in the genetic code can lead to diseases like Tay-Sachs disease, cystic fibrosis, and even color blindness. Modifying these parts of the genome could cure these diseases.

Scientists already have the ability to synthesize, or “write,” segments of DNA from the nucleotides.

This has been done with bacteria, viruses, and yeast. And even shorter pieces of human DNA.

But not fast enough or cheap enough to synthesize the 3 billion base pairs that make up the entire human genome.

The researchers hope the new project will provide the same sort of technological boost to “writing” DNA that the Human Genome Project did for “reading” our genetic structure.

“The primary goal of HGP-write is to reduce the costs of engineering and testing large (0.1 to 100 billion base pairs) genomes in cell lines by over 1,000-fold within 10 years,” the group wrote June 2 in the journal Science.

This would include not just the human genome, but also other organisms important for agriculture, public health, and medical applications.

Read More: Scientists Can Now Edit Your Genome One Letter at a Time »

Challenges to Making It Work

One of the challenges of making this project work is getting the completed genome, or part of the genome, into a host cell. This host could be a mammalian cell or another organism like the bacteria E. coli.

Building a genome from scratch is also a lot different from modifying an existing genome —something that can be done now with technologies like CRISPR/Cas9.

Scientists will need to design the genome so that it keeps the cell working normally. This may be aided by the use of computer software. One of the main players on the project is the computer software company Autodesk.

But more importantly it will require a greater understanding of what every section of the genome does, and scientists are just beginning to scratch the surface.

The group hopes, though, that a “learning by building” approach will help them make progress in this area.

“You know all the parts needed [to make a chromosome], so you take these parts and rebuild it. If it’s functional, you see that you were right,” Torsten Waldminghaus, Ph.D., a synthetic microbiologist at the LOEWE Center for Synthetic Microbiology in Germany, who is not involved in the project, told the Science news.

As happened with the first Human Genome Project, new technologies will need to be developed along the way to speed up the writing process. And to make it cheaper.

The researchers would start by writing smaller segments of the genome and work up to longer pieces. This will eventually have spillover benefits.

“Tangible products may be slow to follow at first, but writing DNA more cheaply and at large scale will make researchers more efficient and comprehensive in their work, leading to practically unlimited potential for indirect products,” Danielle Tullman Ercek, Ph.D., a biochemical engineer at the University of California, Berkeley, told Scientific American.

Read More: Genomics vs. Genetics — A Closer Look »

Uses for Synthetic Human Genome

Possible applications that could come out of this project range from relatively normal to ethically questionable.

One of these pilot projects is the creation of “ultrasafe” cells that are resistant to viruses and cancer.

These could be in the form of stem cells. These are already being tested as a therapy for conditions like rheumatoid arthritis and lung diseases.

Stem cells work to treat disease because they can multiply rapidly. But this is also a trait of cancer cells. One of the lingering concerns over stem cell therapy is that the stem cells will turn cancerous.

This could be avoided by designing stem cells with a synthetic genome that is less likely to mutate and cause cancer.

“A synthetic biology variant encoded to never become cancerous would be preferable,” Paul Freemont, Ph.D., head of the Section of Structural Biology at Imperial College London, told New Scientist.

A synthetic genome could also be used to modify another animal’s genome. Organs from a “humanized” pig could be more suitable for transplant into people — less likely to be rejected by the person’s immune system.

One pilot project even calls for creating a “reference genome” that includes the most common variants of all the genes.

This could be used to test gene variations one by one to see how they affect the function of the body or the development of a disease.

“You could use this blank slate, this plain yogurt of humanity, to slot in the different genes and find out,” George Church, Ph.D., a professor of genetics at Harvard University, told New Scientist.

Read More: Stem Cell Therapy for Rheumatoid Arthritis »

High Cost of Synthetic Genome

The group hopes to launch their project later this year with $100 million in funding from “public, private, philanthropic, industry, and academic sources from around the world.”

Dr. Francis S. Collins, Ph.D., director of the National Institutes of Health (NIH), said the NIH, one of the major funding agencies in the United States, has no plans to fund this kind of project at this time.

In a statement, Collins said that the NIH “has not considered the time to be right for funding a large-scale production-oriented” project like the one being proposed.

The overall cost for the 10-year project will likely be huge, but the group expects it to cost less than the $3 billion spent on the first Human Genome Project.

Some researchers told Nature that the project was needlessly centralizing efforts that are already being done in companies working in this field.

Other critics question whether the group’s stated benefits justify the cost.

“I think developing the tools to make large genetic sequences is an important human goal. Creating an entirely new [human] genomes — that’s a different kind of a project,” Laurie Zoloth, Ph.D., a bioethicist at Northwestern University, told Science.

In an attempt to allay fears that scientists will create a new race of superhumans, the group’s co-leader told Scientific American that cells containing a synthetic genome would be designed so if one is ever grown into a full human, it won’t be able to reproduce.

“We’re not trying to make an army of clones or start a new era of eugenics,” Jef Boeke, Ph.D., a synthetic biologist at NYU Langone Medical Center, told Scientific American. “That is not the plan.”