Complex sentence: It is an artificially constructed chromosome and contains the telomeric, centromeric, and replication origin sequences needed for replication in yeast cells.Extremely useful as one can get eukaryotic protein products with posttranslational modifications.
Split into simpler sentences: It is an artificially constructed chromosome and contains the telomeric, centromeric, and replication origin sequences needed for replication in yeast cells. YACs are extremely useful as one can get eukaryotic protein products with posttranslational modifications.