This application for an ABI Prism 377 Automated DNA Sequencer is being submitted by a group of NIH supported investigators who use DNA sequencing as a significant part of their research effort. They represent a broad-based user group of 128 principal investigators, the majority of which are NIH grantees, whose research depends critically on cost efficient and cost effective DNA sequencing to characterize DNA variation and mutations in natural populations, induced and spontaneous mutants, nad laboratory constructs. Applications are in basic and applied biomedical research including work on humans, dogs, mice, Drosophila, yeast, nematodes, viruses, and plants. Currently, a single ABI 377 automated DNA sequencer is available through a common-use facility for DNA sequencing in Ithaca, serving both the Ithaca campus and the NY City Medical College. It is currently at 81% capacity (more than 2600 sequences per month), and at current rate of growth, will be at maximum capacity within three months (by June 1998). This presents two problems. As capacity is reached, turn-around time will increase, delaying research. Second, in times of machine down-time, all DNA sequencing is shut down. A second ABI Prism 377 DNA Sequencer is requested for this facility to alleviate this situation and move Cornell's BioResource Center closer to an appropriate standard for high throughput DNA sequencing and genotyping for this large group of investigators.