A portion of the coding strand of DNA for a gene has the sequence
5′-...GGAGAGAATGAATCT...-3′
Write out the template DNA strand sequence and polarity as well as the mRNA sequence and polarity for this gene segment.

Question

A portion of the coding strand of DNA for a gene has the sequence

5′-...GGAGAGAATGAATCT...-3′

Write out the template DNA strand sequence and polarity as well as the mRNA sequence and polarity for this gene segment.

Accepted Answer

Hi, everybody. Welcome back. Here's my next question. The following is the M R N A sequence for protein translation. A U G G C U G A U C C U G AC C C U, what is the sequence for the template strand of DNA? And then I have four different answer choices, four different sample strands to pick from. So when I have a question like this, I always like to kind of draw myself a rough diagram to keep straight how the M R N A and two different DNA strands are related to each other in terms of the sequence. So I'm going to draw two blue lines that are going to represent the two strands of DNA, one of them on the top a label template and on the bottom I will label coding slash sense since those are both uh alternate names for that other strand. So to keep this straight, I know that my template strand is the one that my RNA polymerase goes along in transcribing the DNA into an M R N A strand. So on top of my template strand, I'm gonna draw and read my M R N a strand. So that means that M R N A strand and the template strand will have a complimentary sequence to each other. Meanwhile, the M R N A strand and the coding or sense strand will have the same sequence in the same order, except obviously the there will be a T nucleotide in the DNA strand while the R N A has a U. So I like to keep that in mind. So I make sure I'm keeping straight whether I'm supposed to be looking for the same sequence or a complimentary sequence. In this case, I'm given the M R N A sequence and I'm looking for the template strand. So I'm going to be looking for a complimentary sequence with a reminder that I need to have a T complimentary to every A in my R N A strand. So let's start evaluating these answer choices. I'm going to be writing along underneath. I think it's helpful to write down since I'm looking for the complimentary strand. Uh If I were looking for the same sequence, I might just, you know, trace along my answer choices. But when I'm looking for the complimentary sequence, it's pretty easy to get mixed up. So my first three base pairs in my M R N A are a U G. So let's write a three complementary base which would be t complementary to a, a complementary to U and then C complimentary to G. So T AC should be the first nucleotides in my DNA sequence. So let's start with answer choice. A, the first three bases there. A U G. So we can go ahead and cross out choice A as that's not our correct answer. In choice B, those first three bases are indeed T AC. So B is a possibility, still choice C, the first three bases are A T G. So we can go ahead and eliminate choice C and in choice D, the first three base pairs are U AC, not only is that wrong, it has a U in there which you would not find in a DNA strand. So choice D obviously incorrect. Well, I'm in luck, I don't have to go any further. My first three bases have already eliminated three out of four answer choices. So I know that my answer choice must be choice B, so what is the sequence for the template strand of DNA? Given our M R N A sequence? That must be choice BT AC C G AC T A G G AC T G G G A. See you in the next video.

A portion of the coding strand of DNA for a gene has the sequence
5′-...GGAGAGAATGAATCT...-3′
Write out the template DNA strand sequence and polarity as well as the mRNA sequence and polarity for this gene segment.

Verified video answer for a similar problem:

Key Concepts

DNA Strands and Polarity

Transcription Process

Complementary Base Pairing