A cell makes an RNA with the sequence 5′-GGAUCCAUA-3′…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A cell makes an RNA with the sequence 5′-GGAUCCAUA-3′.
- Write the template strand of the DNA that made it, from its 3′ end to its 5′ end.
- Write the coding strand, from its 5′ end to its 3′ end.
- Which of the two strands has the same sequence as the RNA, apart from U and T?
- Which end of the RNA was made first?
Need a reminder? The key ideaShow
The RNA polymerase reads the template strand from 3′ to 5′ and builds the RNA from 5′ to 3′, with U in the place of T. The RNA has the sequence of the coding strand. A hnRNA loses its introns by splicing, gets a cap at the 5′ end and gets a tail of 200 to 300 adenylate residues at the 3′ end.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) Pair each RNA base with a DNA base: G with C, G with C, A with T, U with A, C with G, C with G, A with T, U with A, A with T. The template, from its 3′ end, is 3′-CCTAGGTAT-5′.
Step 2. (b) The coding strand is the partner of the template. It runs the other way, and it is also the RNA with T for U: 5′-GGATCCATA-3′.
Step 3. (c) The coding strand.
Step 4. (d) The polymerase adds nucleotides to the 3′ end of the RNA, so the 5′ end was made first.
Answer: (a) 3′-CCTAGGTAT-5′; (b) 5′-GGATCCATA-3′; (c) the coding strand; (d) the 5′ end.
Check. The two DNA strands pair with each other: C with G, C with G, T with A, A with T, and so on.
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