Answer the following question given this paragraph: 

Watch this short video (http://openstaxcollege. org/l/transgenic) explaining how scientists create a transgenic animal. Although the classic methods of studying the function of genes began with a given phenotype and determined the genetic basis of that phenotype, modern techniques allow researchers to start at the DNA sequence level and ask: "What does this gene or DNA element do?" This technique, called reverse genetics, has resulted in reversing the classical genetic methodology. One example of this method is analogous to damaging a body part to determine its function. An insect that loses a wing cannot fly, which means that the wing’s function is flight. The classic genetic method compares insects that cannot fly with insects that can fly, and observes that the non-flying insects have lost wings. Similarly in a reverse genetics approach, mutating or deleting genes provides researchers with clues about gene function. Alternately, reverse genetics can be used to cause a gene to overexpress itself to determine what phenotypic effects may occur.


Q: Which kind of genetics approach involves mutating or deleting genes provides researchers with clues about gene function?

 Choices:

- possible genetics

- impossible genetics

- inverse genetics

- reverse genetics

A:
reverse genetics
