Aside from the diamond, the ruby, sapphire, emerald, pearl (not, strictly speaking, a gemstone) and opal have also been considered to be precious. Up to the discoveries of bulk amethyst in Brazil in the 19th century, amethyst was considered a precious stone as well, going back to ancient Greece.
A restriction map is a map of known restriction sites within a sequence of DNA. Restriction mapping requires the use of restriction enzymes.In molecular biology, restriction maps are used as a reference to engineer plasmids or other relatively short pieces of DNA, and sometimes for longer genomic DNA.ased on the sizes of the resultant DNA fragments the positions of the sites can be inferred. Restriction mapping is a very useful technique when used for determining the orientation of an insert in a cloning vector, by mapping the position of an off-center restriction site in the insert (Dale, Von Schantz, 2003).
1 A linear map is a homomorphism that preserves the vector space structure, namely the abelian group structure and scalar multiplication. 2  The scalar type must further be specified to specify the homomorphism, e.g. every R-linear map is a Z-linear map, but not vice versa.ince inverses exist in G and H, one can show that the identity of G maps to the identity of H and that inverses are preserved. The algebraic structure to be preserved may include more than one operation, and a homomorphism is required to preserve each operation.