What is a controlled variable in an experiment? a
b
A factor that is purposely left the same.
A factor that is purposely changed and being measured.
A factor that will be observed and measured.
A factor that is purposely being changed.
С
d A factor that is purposely being changed

A factor that is purposely left the same.

Explanation:

A controlled variable should not be changed throughout an experiment or else it will affect the outcome of each individual trial.

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.