Pairing (c) joined a wild-type mouse with one that was a mutant for the db gene.
In this experiment, mice were paired together based on specific genotypes. Let's analyze each pairing option:
Pairing (a): Joined two mice that were mutants for both the ob and db genes. This means that both mice had mutations in both genes.
Pairing (b): Joined two mice that were mutants for the ob gene but wild-type for the db gene. This means that both mice had mutations only in the ob gene.
Pairing (c): Joined a wild-type mouse with one that was a mutant for the db gene. This means that one mouse had a mutation in the db gene while the other mouse had the normal or wild-type gene.
Pairing (d): Joined a wild-type mouse with one that was a mutant for the db gene. This means that one mouse had a mutation in the db gene while the other mouse had the normal or wild-type gene.
Based on the information provided, the correct statement about the genotype pairings would be pairing (c): joined a wild-type mouse with one that was a mutant for the db gene.