Place the steps of transcription in order:

1. rna polymerase attaches to the dna template

2. the mrna strand moves out of the nucleus

3. base pairing forms mrna

4. the dna strand separates

example: 2,3,4,1

4. The DNA strand separates

1. RNA polymerase attaches to the DNA template

3. Base pairing forms mRNA

2. The mRNA strand moves out of the nucleus

during the process of dna replication, brdu can replace thymidine and incorporate into the newly synthesized dna, cell proliferation thus can be reflected in the extent of brdu incorporation.