Chapter 30, Problem 1P

Interpretation Introduction

Interpretation: The sequence of the DNA coding strand and DNA template strand for the following mRNA sequence should be determined:

5’-AUGGGGAACAGCAAGAGUGGGGCCCUGUCCAAGGAG-3’

Concept introduction:

DNA stores genetic information in a stable form that can be readily replicated.

The template strand is DNA strand from which mRNA is built and it serves as a template for transcription. It runs in a 3’ to 5’ direction.

The DNA strand which is not used as template for transcription is said to be a coding strand as it corresponds to the same sequence as that of mRNA, the only difference is instead of thymine, uracil is present in mRNA strand.

Answer to Problem 1P

For the given RNA sequence, the sequence of the coding strand is 5’-ATGGGGAACAGCAAGAGTGGGGCCCTGTCCAAGGAG-3’ and the sequence for the template strand is 3’-TACCCCTTGTCGTTCTCACCCCGGGACAGGTTCCTC-5’.

Explanation of Solution

If the left chain is the coding chain, one reads from the 5’ end above downwards. So, the code is read as ‘…ATTGC…’ in this small part of the gene.

The template strand and the coding strand are complementary to each other, that is for each ‘A’ on the coding strand there is a ‘T’ on the template strand. For every ‘G’ on the coding strand there is a ‘C’ on the template strand. As in DNA replication, when a template strand is taken and a new strand is constructed, a photocopy of the original DNA coding strand is obtained. Similarly, when an RNA strand is constructed on the template strand, a copy of the DNA coding strand is obtained except for the difference of uracil being used instead of thymine in RNA. Thus, if the original DNA strand has the sequence ‘ATTGCT’, then it would get converted to ‘AUUGCU’ where everything is similar except for the replacement of ‘T’ by ‘U’.

Thus, the answer, the sequence for the coding strand for given RNA sequence, the sequence of the coding strand is 5’-ATGGGGAACAGCAAGAGTGGGGCCCTGTCCAAGGAG-3’ and the sequence for the template strand is 3’-TACCCCTTGTCGTTCTCACCCCGGGACAGGTTCCTC-5’.

Conclusion

For the given RNA sequence, the sequence of the coding strand is 5’-ATGGGGAACAGCAAGAGTGGGGCCCTGTCCAAGGAG-3’ and the sequence for the template strand is 3’-TACCCCTTGTCGTTCTCACCCCGGGACAGGTTCCTC-5’.