A test that is used to determine if the mutation associated with a given phenotype is due to mutations in two different genes or due to different alleles of the same gene is called a complementation test.
A complementation test is also called as a cis-trans test.
If the mutations in a complementation test are located on the same position then the genes are termed as being on the cis position otherwise on the trans-position.
A cis test, that is if the genes are located on the same position serves as a control for the complementation test.
The nervous system is made up of the brain, spinal cord and nerves. The spinal cord helps carry messages or signals back and forth between your body and brain.