Astronomers have seen stars forming within a nebular cloud. as the nebular cloud condenses and its own gravitational attraction collapses it, heat and energy build up creating

nuclear fusion

Explanation:

Nuclear fusion is a stage that happens during star formation. This begins in the gravitational collapse of a giant nebula cloud. These clouds can span several dozen cubic light years of space and contain large amounts of matter. When gravity collapses the cloud, heat and energy accumulate, the cloud splits into smaller pieces, each centered around a concentration of matter. As these concentrations increase in mass, gravitation corresponds, and with it the whole process accelerates, with the collapse itself creating thermal energy.

Eventually, these parts condense under heat and pressure into gaseous spheres called proto-stars. If a proto-star does not concentrate enough mass, it never reaches the pressure and heat necessary for nuclear fusion, and becomes a brown dwarf.

step 1: initiation

initiation is the beginning of transcription. it occurs when the enzyme rna polymerase binds to a region of a gene called the promoter. this signals the dna to unwind so the enzyme can ‘‘read’’ the bases in one of the dna strands. the enzyme is now ready to make a strand of mrna with a complementary sequence of bases.

step 2: elongation

elongation is the addition of nucleotides to the mrna strand. rna polymerase reads the unwound dna strand and builds the mrna molecule, using complementary base pairs. there is a brief time during this process when the newly formed rna is bound to the unwound dna. during this process, an adenine (a) in the dna binds to an uracil (u) in the rna.

step 3: termination

termination is the ending of transcription, and occurs when rna polymerase crosses a stop (termination) sequence in the gene. the mrna strand is complete, and it detaches from dna.