CRISPR gene editing has just pulled off one of its most impressive feats yet. A team of scientists from China has managed to create a new species: a baker’s yeast with just one mega-chromosome. Meanwhile, a group of American researchers has done the same thing using two chromosomes instead of one.
Why is this so cool? Well, this beer-making microorganism usually has 16 chromosomes. All of this genetic information is now squished into a single chromosome. The pioneering research could help explain why we, and other organisms, split our DNA across many different chromosomes. As this freak yeast shows, it doesn’t actually appear to make much difference if the DNA is in one chromosome or 16 chromosomes.
“That was the biggest shocker – that you can just get away with this and yeast seem to shrug its shoulders,” Jef Boeke, a geneticist at New York University who worked on the US project, told Nature News.
The scientists’ research, along with an accompanying essay, was published in the journal Nature on August 1. The US study can be read here, and the Chinese study can be viewed here. The researchers used CRISPR-Cas9, a kind of “cut-and-paste” gene-editing tool, to snip the chromosomes’ centromeres and telomeres, which hold each stringy chromosome together. They then stitched them back together in a single chain.
Yeast is a type of eukaryote, a group that also includes humans, plants, and animals. Weirdly, the number of chromosomes a eukaryote has doesn’t seem to be associated with the amount of genetic information it contains or how “complex” the creature is. A carrot has 18 chromosomes, a kangaroo has 16, a carp has 100, a great white shark has 82, and an atlas blue butterfly has 450.
The fact that changing the number of chromosomes around doesn’t appear to change the action of the genes in them suggests that the number of chromosomes is simply a random accident of evolution.
“We found that yeast can tolerate drastic changes in chromosome number without disrupting the action of the genes in them, more evidence of their robustness as an engineering platform,” Boeke explained in a statement.
The new yeast did run into some trouble when it came to sexual reproduction. Nevertheless, technically speaking, the Synthetic Yeast 2.0 could be a totally new human-made species as it can’t reproduce with the un-altered yeast at all.
“Beyond applications, this work sheds light on the wild trajectory of accidental chromosome duplications and fusions across evolution that has left one ant species with a single pair of chromosomes, humans with 23 pairs, and one species of butterfly with 220,” said Boeke.
“We are learning how one species becomes two.”