Final answer:
The term describing a syndrome caused by the deletion of multiple, neighboring genes is Contiguous gene syndrome.
Step-by-step explanation:
The term used to describe a syndrome caused by the deletion of multiple, neighboring genes is D. Contiguous gene syndrome. In contrast to disorders caused by a mutation in a single gene or by an incorrect number of chromosomes, contiguous gene syndromes involve the deletion of a series of genes located next to each other on a chromosome. As a result, the phenotype reflects the loss of several gene products. This differs from haploinsufficiency, which refers to a case where a single copy of a gene is not sufficient to produce a normal phenotype. Down syndrome, caused by trisomy 21, is an example of a disorder due to an abnormal number of chromosomes, but does not fit the definition of a contiguous gene syndrome.