Physical Mapping 



Abstracts 



Human Chromosome 21: Linkage Mapping and Cloning 

 DNA in Yeast Artificial Chromosomes 



S. E. Antonarakis, P. A. Hieter. and M. K. McCormick 



Center for Medical Genetics. The Johns Hopkins University School of Medicine, 



Baltimore, MD 21218-2608 



(301)935-7872 



The goal of our research is to contribute to the cloning of human chromosome 21 DNA 

 in yeast artificial chromosomes (YACs). Chromosome 21 is the smallest human 

 chromosome and contains about 1.4% of the human genome. The cloning of human 

 DNA in YACs (Burke et al.. Science 236, 806-812, 1987) allows large fragments of 

 DNA ( 100-1000 kb) to exist as additional chromosomes in S. cerevisiae. We used new 

 YAC cloning vectors that facilitate the manipulation and mapping of the resulting 

 YACs. DNA from cell line WA 17 (a mouse-human hybrid with chromosome 21 as the 

 only human material) and from flow-sorted chromosome 21 were used as the starting 

 material. Size-selected DNA from complete Ni>t I or partial EcoR I digestion was 

 ligated to the vectors, and yeast spheroplasts were transformed in the presence of 

 polyamines to eliminate a bias in favor of smaller DNA inserts. In our initial 

 experiments, YACs have been obtained from both DNA sources; the average size of 

 those from the WA-17 cell line was 410 kb. 



Specific future research goals include mapping the YAC clones and scaling up the 

 experiments in order to obtain a large number of YACs, linking the YACs in 

 overlapping contigs. and constructing a macrorestriction map of chromosome 21. 



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