Question

is there a sentence fragment? when scientists sequenced the dna of domestic cats, they made a startling discovery. a remarkable similarity between the genomes of house cats and those of their feline relatives in the wild. yes no

Explanation:

The second part "A remarkable similarity between the genomes of house cats and those of their feline relatives in the wild" is a fragment as it lacks a verb and a complete thought - it is a noun phrase. The first part "When scientists sequenced the DNA of domestic cats, they made a startling discovery" is a complete sentence.

Answer:

yes