Scientists in an international team have synthesized 16 chromosomes for yeast. Before this, the only synthetic DNA had been designed for organisms like bacteria, which are simpler in their genetic makeup.

Yeast cells have a nucleus and are related to plants and animals. They have 2,000 genes similar to those of humans.

This new creation is vital to the evolving science of synthetic biology. Scientists replaced genes in the original chromosome with the manmade ones, which were successful in integration into the yeast cell.

The scientists designed and created 273,871 pairs of DNA, less than the 316,667 pairs in the original chromosome. They sorted and removed the unnecessary DNA that was not coded for any proteins.

Scientists made more than 50,000 changes to the DNA code in the chromosome, and the yeast gained new functions.

One new function is a chemical switch that allows researchers to change a chromosome into different variations, making genetic manipulations easier for researchers.

Scientists hope they can use this new break in synthetic biology to produce vaccines and more sustainable forms of biofuel.

Critics are arguing that this new science is meddling with nature and the effects are unknown. The researchers of synthetic biology said these new organisms are designed with built-in restrictions; for instance, these strains of yeast cannot survive outside a lab environment.

This is one step closer to researchers being able to synthesize eukaryotic genomes, which include plant and animal genomes.