you're using the word 'range' as a sort of collective noun for more than one tissue. While the word range appears to be singular therefore requiring 'is', as it is describing an object that is in the plural, rather than being used as a noun (driving range, etc) you should use 'are'.
you're using the word 'range' as a sort of collective noun for more than one tissue. While the word range appears to be singular therefore requiring 'is', as it is describing an object that is in the plural, rather than being used as a noun (driving range, etc) you should use 'are'.