Like some genes is a term that refers to certain types of genetic traits. Mutants (6 letters) are genes that have undergone a change in their structure or function, usually resulting in a different phenotype. Recessive (9 letters) genes are those that are not expressed in the phenotype unless two copies of the gene are present. Sex-linked (9 letters) genes are those that are located on the sex chromosomes and are therefore inherited differently in males and females.