By manipulating chromosomes, we intend to create new genetic constructs that exhibit commercially useful traits. Triploids, organisms with three sets of chromosomes instead of the normal two sets, for example, are useful in shellfish aquaculture. Triploid shellfish have several advantages over normal diploids, including sterility, faster growth, improved meat quality and increased disease resistance during the spawning season. The development of tetraploid oysters has revolutionized triploid production for the oyster culture industry. A newly fertilized egg of the Pacific oyster with polar body I, II, maternal and paternal chromosome groups, all of which can be artificially manipulated to produce polyploid and aneuploid oysters.
Research is also underway on the production and isolation of certain aneuploids.
Aneuploids are organisms with incomplete sets of chromosomes. Five trisomic families have been isolated in 1997, and further research is being conducted to produce more and evaluate the phenotypic expression of trisomics. Metaphases from polyploid and aneuploid Pacific oysters produced by chromosome manipulation. The normal diploid number is 20.