Final answer:
The sequences not expected to overlap at all would be from a brain genomic library and a muscle cDNA library or vice versa since different genes are expressed in different tissues.
Step-by-step explanation:
Sequences from different types of libraries can be expected to either overlap or not overlap depending on whether they represent the same regions of DNA or RNA from an organism. Genomic libraries contain all the genomic DNA of an organism, hence any two genomic libraries from the same organism (brain and muscle) will have overlapping sequences. However, cDNA libraries reflect the expressed genes in different tissues, and so a brain cDNA library will contain sequences not expressed and hence not present in a muscle cDNA library and vice versa.
A genomic library and a cDNA library from the same tissue (e.g., muscle) will have some sequences that overlap, specifically those that are expressed in that tissue and thus present in both libraries. Therefore, the sequences that would be expected not to overlap at all would be between a genomic library from one tissue (brain) and a cDNA library from a completely different tissue (muscle), indicating that there are unique sequences expressed in each tissue that are not shared between the two.