Question

When a stop codon is reached, the RNA strand separates from the DNA molecule, leaves the nucleus, and goes through the nuclear membrane into the cytoplasm The two strands of DNA separate at that location. An enzyme attaches to the DNA molecule at the gene of interest. The two DNA strands rejoin Complementary RNA nucleotides bond to the nitrogenous bases on one of the separated DNA strands. The chain of RNA nucleotides forms a single-stranded molecule of RNA by using the DNA strand as a template.

Answer 1

The correct order of the events is:

1. An enzyme (RNA polymerase) binds to the parent DNA molecule or gene of interest. This is the first step of transcription-initiation. RNA polymerase binds to DNA region called promotor.

2. The double stranded-DNA gets separated at the location where the enzyme attaches. This event is also part of the initiation step. DNA is unwinded so the enzyme can ‘‘read’’ the bases in one of the DNA strands.

3. RNA nucleotides, complementary to nucleotides present in the parent DNA molecule, make bonds with the bases on a leading strand of the DNA. This is the second step of the transcription-elongation. Elongation is the addition of nucleotides to the new formed RNA strand (mRNA).

4. The RNA nucleotide chain forms an SS RNA (single-stranded RNA) molecule with the use of a DNA strand as a template. This is the formation of mRNA thanks to complementary DNA strand.

5. When a stop codon is reached, the RNA strand gets separated from the parent DNA molecule, leaves the nucleus, and enters the cytoplasm. This is the last step of the transcription-termination, when RNA polymerase crosses a stop sequence in the gene. When the mRNA is formed, it detaches from DNA.                                      

6. During the final step, the separated strands of DNA rejoin.