The following is a portion of an mRNA sequence:
3'-AUCGUCAUGCAGA-5'
During transcription, was the adenine at the left-hand side of the sequence the first or the last nucleotide used to build the portion of mRNA shown? Explain how you know.

Question

The following is a portion of an mRNA sequence:

3'-AUCGUCAUGCAGA-5'

During transcription, was the adenine at the left-hand side of the sequence the first or the last nucleotide used to build the portion of mRNA shown? Explain how you know.

Accepted Answer

Hey, everyone. Let's take a look at this question together during transcription of the M R N A sequence. Three A U C G U C A U G C A G A five was the adenine at the left hand side. The 1st, 2nd, 3rd or last nucleotide used to build the portion of M R N A shown is it answer choice. A, the first nucleotide used answer choice B the second nucleotide used answer choice C the third nucleotide used or answer choice D the last nucleotide used, let's work this problem out together to try to figure out if the adenine on the left hand side of the M R N A sequence was the 1st, 2nd, 3rd or last nucleotide used to build the sequence. So when it comes to transcription of M R N A sequences, we know that the enzyme R N A B liras synthesizes the M R N A molecule in the five N 23 N direction, which means that R N A polymerase adds nuclear tides to the three end of the growing chain. And so the three end is the end of the sequence. And in the case of the M R N A sequence that we have here, we have that three end and then we have a U C and then the rest of the sequence until that five end. And since this adenine is closest to that three end of the sequence, and we know that the three end is the end of the sequence. That means that the adenine at the left hand side of the M R N A sequence was the last nucleotide used to build the portion of this M R N A sequence. So answer choice D, the last nucleotide used is the correct answer. Since we know that R N A polymerase synthesizes this M R N A sequence and it synthesizes the sequence in the 5 to 3 direction, which means that the three end is the end of the sequence. And so the adenine closest to the three end at the left hand side of the sequence was the last nucleotide used to build the portion of this M R N A sequence. So answer choice D is the correct answer. I hope you found this video to be helpful. Thank you and goodbye.

The following is a portion of an mRNA sequence:
3'-AUCGUCAUGCAGA-5'
During transcription, was the adenine at the left-hand side of the sequence the first or the last nucleotide used to build the portion of mRNA shown? Explain how you know.

Verified video answer for a similar problem:

Key Concepts

Transcription Process

mRNA Orientation

Nucleotide Addition