Online Education Kit: 1980's
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On Other Sites: Cloning into a Yeast Artificial Chromosome (YAC)
Step-by-step description

1987: YACs Developed

Illustration of YACsYeast artificial chromosomes (YAC) can carry large segments of DNA from other species, like humans.

A YAC is copied reliably when a yeast cell divides. Plasmids - pieces of DNA in bacteria that can carry foreign DNA - and viruses are also used in the lab to store and copy fragments of human DNA. But YACs can carry million base-pair-long fragments of human DNA, whereas plasmids and viruses carry a few thousand base-pair-long pieces only. Being able to deal with bigger fragments of DNA made mapping the human genome easier, especially when scientists still had relatively few landmarks to navigate by.

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Last Reviewed: April 26, 2013