While exploring a coal mine, scientists found plant fossils in the ceiling of the mine which had been preserved by an earthquake. samples taken from one of the fossils have carbon-14 activities of 40.0 counts/min. a reference sample of the same size, from a plant alive today, has a carbon-14 activity of 160.0 counts/min. if carbon-14 has a half-life of 5730 years, what is the age of the plant fossil in years?

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.

a. by using fur or clothes to trap heat energy near the body