The DNA sequence below gives the first 12 base pairs of ...

Question

The DNA sequence below gives the first 12 base pairs of the transcribed region of a gene, and the template and nontemplate strands of DNA are identified. The transcription start is the thymine nucleotide at the end of the sequence given. Use the diagram to answer the list of questions. Make a copy of the diagram before you begin answering the questions, or have one group member diagram the answers for bacteria and another group member diagram the answers for eukaryotes.

Nontemplate strand ___________TTGCTACGGTCA___________
Template strand ___________AACGATGCCAGT___________

Give the mRNA transcript sequence and the polarity of the transcript.

Accepted Answer

Welcome back, everyone. Let's look at the next problem. The DNA sequence below gives the 1st 14 base pairs of the transcribed region of a gene and the template and non template strands of DNA are identified. Now, we have our non template strand listed here and then our template strand, then the question says, what is the M R N A transcript sequence? And we have four different answer choices and we need to figure out which of them is the M R N A transcript that would result from the given non template strand and template strand. So first of all, we have to remember which strand our M R N A is going to be complimentary to and which will be in the same order. So we know that the M R N A is transcribed from the template stranded. And that makes sense since it's a template for the M R N A and is therefore complimentary to the template, meaning it's in the same order in terms of the base pairs that are there or excuse me, not base pairs, it's R N A the same bases that are there the same order as the non template strand, which is why that strand is often called the coding or sense strand. And the last thing we just have to remember is that the M R N A strand will have U instead of T. So we can go follow along our non template strand just remembering the substitute A U everywhere there's A T. So when we look at our non template strand, we see that it starts with A T. So we expect our M R N A transcript to start with A U. So let's go ahead and rule out the two strands here that do not start with a U. Choice A starts with an A and Joyce C also starts with an A. So let's look at our first three bases, our T AC on the non template strand. So we'd expect to see U AC on our M R N A transcript. So choice B has U U ac. Well, choice D has U AC. So it looks like choice D is going to be our correct answer. We can just double check and follow along, make sure it continues to be correct. We then have G C T. So we'd expect to see G C U which we do see in choice D and then a G T. So we'd see a G U and Joy D and then C A G. In choice D, we have C A G and then around temple trans as TT our choice do you hear ends just with a single U? But all the bases we have are in the same matching bases to the non template strand. So choice D is our correct answer. We can eliminate choice B which isn't quite correct. And we know that our M R N A transcript and choice D is U AC G C U A G U C A G U. See you in the next video.

Key Concepts

Transcription

Template and Nontemplate Strands

Polarity of RNA Transcript

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