Question

When working on barley plants, two researchers independently identify a short-plant mutation and develop homozygous recessive lines of short plants. Careful measurements of the height of mutant short plants versus normal tall plants indicate that the two mutant lines have the same height. How would you determine if these two mutant lines carry mutation of the same gene or of different genes?

Answer 1

Answer:

In the given case, the two scientists are working on a barley plant, independently determined a short plant mutation, and thus, created homozygous recessive lines of short plants. The measurements of the normal tall plants' height in comparison to the mutant short plants were performed carefully, which showed that the two mutant lines were having similar height.  

In order to test whether these two mutant lines are carrying mutation of similar genes or of the distinct genes, complementation test is performed. In the test, it was found that the tall nature is dominant over the short. The complementation test takes place when the two strains of the organism exhibiting different homozygous recessive mutations generate the same phenotype, which is mutant and is also generating the wild type offspring when mated or crossed because of recessive mutation.  

Complementation will take place only when there is a mutation in different genes. In the given case because of the wild type offspring, a complementation test will take place showing mutation of distinct genes. When the two strains are identical, there will be no generation of wild-type offspring because of which complementation test will not take place.