Example of a human geneticdisorder caused by an alteration in
chromosome structure (not a modification of an allele).

Cri du chat syndrome.

Explanation:

Maintenance of chromosomal structure is important for the proper functioning of the cell. The alteration or change in the chromosome structure may leads to the various genetic problem.

The cri du chat syndrome occurs due to the missing of the short arm of the chromosome number 5. The deletion in short arm of chromosome 5 is responsible for this syndrome. The infants that suffer from this syndrome has high pitched cry that is similar to the cry of a cat.

Thus, the answer is Cri du chat syndrome.

answer and explanation;

volcanic rocks are igneous rocks which form from lava, molten rock which has been thrust out of a volcano onto the surface of a rocky body such as an asteroid, planet, or dwarf planet.  

plutonic rocks are igneous rocks which form from subterranean chambers of molten rock or magma. plutonic rocks make up the base of continental crust as well as oceanic crust. their slow rate of formation causes them to be coarse grained since there is plenty of time for large crystals to form before the magma solidifies into rock.

the textural difference is that plutonic rocks are more coarse grained than volcanic rocks. plutonic rocks are coarse grained while volcanic are fine grained ; glassey or fragmental. since fine and coarse are adjectives the decision as to whether a rock is fine or coarse grained is generally made on the bases of whether or not the individual crystals can be seen in most if the rock.