Answer:
According to the modern theory of stellar evolution, the sun is heated to the enormous temperatures at which nuclear fusion can occur by gravitational energy released as the solar mass contracts from an initially large gas cloud
Explanation:
The given blank can be filled with forward genetics.
Forward genetic screen or forward genetics refers to a method used to determine a set of genes or genes accountable for a specific phenotype of a species. On the other hand, reverse genetics or reverse genetic screen evaluates the phenotype of a species following the disruption of a known gene.
The method of forward genetics was initially done by inducing mutants with radiation, by using naturally occurring mutations, insertional mutagenesis, or chemicals.