To determine whether curl is dominant or recessive, cross a curl cat with a non-curl cat from far away (very unlikely to have the curl allele). If it is dominant, this is a test cross and all progeny should have curl. If it is recessive, then all of the progeny will lack curl. To get true breeding curl cats, cross among progeny and select for several generations for curl production, then test, as originally, for curl homozygosity by crossing with non-curl cats.
Work Step by Step
This question asks you to put together several concepts from the text (skim to review) including true breeding/homozygosity and test crosses. Use your imagination to go through the two cases (curl dominant, curl recessive).