neochromosome

A neochromosome is an engineered chromosome that functions as an additional genetic element inside a host cell, carrying genetic material separate from the organism's native chromosomes. Designed to be stably inherited, neochromosomes typically include chromosomal features such as centromeres, telomeres, and autonomous replication origins, enabling replication and mitotic segregation much like a natural chromosome. They are distinguished from plasmids by their size, stability, and capacity to host large gene sets.

Construction and design: Neochromosomes are assembled from many DNA fragments and integrated as a discrete chromosome. In practice they are built with a centromeric sequence, telomeres at the ends, and replication origins, and then introduced into the host by transformation or genome integration. The fragments can encode multiple enzymes and regulatory elements, enabling complex metabolic pathways or trait libraries. In organisms such as Saccharomyces cerevisiae, in vivo assembly and recombination are commonly used to construct neochromosomes.

Applications: They are used mainly in metabolic engineering and synthetic biology to host large multi-gene pathways, enabling modular construction and testing of complex traits or production strains. Potential applications include production of pharmaceuticals, biofuels, and specialty chemicals, as well as fundamental studies in chromosome biology and inheritance.

Challenges: Key issues include stability and faithful segregation across cell divisions, control of gene dosage, metabolic burden on the host, and potential rearrangements. Delivery and maintenance can be species-dependent, and there are biosafety and regulatory considerations for synthetic chromosomes.

Related topics include artificial chromosomes, yeast artificial chromosomes, chromosome engineering, and synthetic biology.