Final answer:
A cosmid vector is created by combining viral DNA fragments and plasmid fragments, allowing for the insertion and cloning of large DNA segments up to 40 Kb, which is useful for creating genomic libraries.
Step-by-step explanation:
The vector created by the combination of viral DNA fragments and fragments from a plasmid is known as a cosmid vector. Cosmids utilize the phage lambda cos site to facilitate the insertion and cloning of large DNA fragments, which can be up to 40 Kb in size. They combine the high DNA capacity of bacteriophages with the convenience and ease of use of plasmids. This makes cosmids a powerful tool in constructing genomic libraries, where an entire individual organism's DNA is represented, allowing the study of large eukaryotic genomes. Cosmids have distinctive features such as a drug resistance marker, plasmid origin of replication, and the lambda cos site which are crucial for their identification and function.