<n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-definition>chromosome found in a trisomic state in the cells of persons with Down syndrome.</n0:def-definition><n0:def-source>CSP2000</n0:def-source></n0:ComplexDefinition><n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-definition>One of the two pairs in the seventh group (or group G) of human chromosomes according to the current classification for humans.</n0:def-definition><n0:def-source>MSH2001</n0:def-source></n0:ComplexDefinition>
<n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-definition>The designation for each member of the second smallest human autosomal chromosome pair. Chromosome 21 spans around 47 million nucleotides and represents about 1.5% of the total DNA in normal diploid cells.</n0:def-definition><n0:def-source>NCI</n0:def-source></n0:ComplexDefinition>