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A new map shows that human chromosome 21q consists of a continuous assemblage of clones that overlap each other. The map was derived from human yeast artificial chromosomes for which sequence-tagged sites served as landmarks that were located by polymerase chain reaction. The yeast artificial contiguous unit begins with pericentromeric loci and terminates with subtelomeric loci of 21q. The map agrees with other physical and genetic mapping evidence and should lead to further research on the form and purpose of particular chromosomes.

Cephalopods are key species of the eastern Arctic marine food web, both as prey and predator. Their presence in the diets of Arctic fish, birds and mammals illustrates their trophic importance. There has been considerable research on cephalopods (primarily Gonatus fabricii) from the north Atlantic and the west side of Greenland, where they are considered a potential fishery and are taken as a by-catch. By contrast, data on the biogeography of Arctic cephalopods are still incomplete. This study integrates most known locations of Arctic cephalopods in an attempt to locate potential areas of interest for cephalopods, and the predators that feed on them. International and national databases, museum collections, government reports, published articles and personal communications were used to develop distribution maps. Species common to the Canadian Arctic include: G. fabricii, Rossia moelleri, R. palpebrosa and Bathypolypus arcticus. Cirroteuthis muelleri is abundant in the waters off Alaska, Davis Strait and Baffin Bay. Although distribution data are still incomplete, groupings of cephalopods were found in some areas that may be correlated with oceanographic variables. Understanding species distributions and their interactions within the ecosystem is important to the study of a warming Arctic Ocean and the selection of marine protected areas. [ABSTRACT FROM AUTHOR]