One of the greatest ethical debates in science - manipulating the fundamental building blocks of life - is set to heat up once more.

According to scientists behind an ambitious and controversial plan to write the human genome from the ground up, synthesising DNA and incorporating it into mammalian and even human cells could be as little as four to five years away.

Nearly 200 leading researchers in genetics and bioengineering are expected to attend a meeting in New York City next week, to discuss the next stages of what is now called the Genome Project-write (GP-write) plan: a US$100 million venture to research, engineer, and test living systems of model organisms, including the human genome.

Framed as a follow-up to the pioneering Human Genome Project (HGP) – which culminated in 2003 after 13 years of research that mapped the human genetic code – this project is billed as the logical next step, where scientists will learn how to cost-effectively synthesise plant, animal, and eventually human DNA.

"HGP allowed us to read the genome, but we still don't completely understand it," GP-write coordinator Nancy J. Kelley told Alex Ossola at CNBC.

While those involved are eager to portray the project as an open, international collaboration designed to further our understandings of genome science, GP-write provoked considerable controversy after its first large meet-up a year ago was conducted virtually in secret, with a select group of invite-only experts holding talks behind closed doors.

"Given that human genome synthesis is a technology that can completely redefine the core of what now joins all of humanity together as a species, we argue that discussions of making such capacities real ... should not take place without open and advance consideration of whether it is morally right to proceed," medical ethicist Laurie Zoloth from Northwestern University and synthetic biologist Drew Endy of Stanford University wrote at the time for Cosmos Magazine.

Since then, the researchers behind the initiative have been more candid, announcing details of the project in a paper in Science, as well as releasing a white paper outlining GP-write's timeline and goals.

One of GP-write's lead scientists – geneticist and biochemist Jef Boeke from NYU Langone Medical Centre – says the approach has always been to consult the scientific community at large, to help frame and steer the research as it develops.

"I think articulation of our plan not to start right off synthesising a full human genome tomorrow was helpful. We have a four- to five-year period where there can be plenty of time for debate about the wisdom of that, whether resources should be put in that direction or in another," he told CNBC.

"Whenever it's human, everyone has an opinion and wants their voice to be heard. We want to hear what people have to say."

But while that conversation is taking place, the science is developing regardless.

In March, Boeke shared details on a related project he's involved with, where he oversees hundreds of scientists who are working together to synthesise an artificial yeast genome, which is expected to be complete by the end of 2017.

There might be a large gap between successfully synthesising yeast DNA and creating artificial human DNA from scratch. But the overall goal is to figure out how to synthesise comparatively simple genetic codes (such as microbial and plant DNA), before moving on to the ultimate prize.

"If you do that, you gain a much deeper understanding of how a complicated apparatus goes," says Boeke. "Really, a synthetic genome is an engine for learning new information."

Under its new organisational structure, GP-write is the parent project, which encompasses the core area of Human Genome Project-write (HGP-write), focussed on synthesising human genomes in whole or in part.

In addition to synthesising plant, animal, and human DNA, the primary goal of the project is to lower the cost of engineering genomes.

At present, it's estimated to cost about 10 US cents to synthesise every base pair of nucleobase molecules that make up our DNA – and given humans have about 3 billion of these pairs, that makes for some pretty prohibitively expensive synthesis.

The plan is to reduce this cost by more than 1,000-fold within 10 years.

If that happens, the lower expense involved in synthesising DNA could unlock all kinds of new potential medical treatments – targeting illnesses such as cancer and genetic diseases, helping the body to accept organ transplants, and learning more about immunity to viruses.

Of course, before that can happen, GP-write's organisers need to raise an estimated US$100 million in funding – which will be another of the drivers of next week's get together.

It's an incredibly exciting undertaking, although there's bound to be more controversy as GP-write marches ahead.