Question

A researcher conducted studies on proteins obtained from mouse livers. He discovered a novel protein and decided to obtain its genetic origins. The mRNA sequence he found was AUUCGGUACUGUACUAGC. What is the sequence of the strand that wasn’t used for RNA synthesis?
TTTGCTATACTATAGTAC

ATTCGGTACTGTACTAGC

ATCGGTCTAGTACGATCG

ATGTCTATACTAGCTTTT

ATGTCTATGGGTAGCTTT

Answer 1

The sequence of the strand that wasn't used in the process of RNA synthesis is ATTCGGTACTGTACTAGC.

Proteins are formed through the process of translation, during which an mRNA strand is turned into an amino-acid sequence, which then makes up the structure of the protein. The process of transcription precedes translation, and in this process, a DNA strand which holds information about the protein that needs to be produced, is transcribed into an mRNA strand. So the mRNA strand is complementary to the DNA strand it was transcribed from.

The base pairs that are found in the DNA are A-T and G-C, while in RNA, they are A-U, and G-C. For example, if the DNA strand TCAA was to be transcribed into RNA, the mRNA sequence would be AGUU, which is complementary to that of the DNA.

DNA is a molecule that is double-stranded, so it has two strands, held together by hydrogen bonds, and these strands are antiparallel, so the two strands are complementary to one another.

You can get to the solution of your question by finding the complementary strand to the mRNA strand in question, which is:

AUUCGGUACUGUACUAGC⇒
TAAGCCATGACATGATCG

This is the DNA strand that was used in RNA synthesis in the process of transcription. The sequence of the strand that wasn't used for RNA synthesis can be determined from the one that was used, by finding the sequence that is complementary to it:
TAAGCCATGACATGATCG⇒ATTCGGTACTGTACTAGC

This is the sequence of the DNA strand that is complementary to the one that was used in the process of transcription for the synthesis of the RNA strand, so this is the sequence of the strand that wasn't used in the process of RNA synthesis.

Answer 2

Answer:

ATTCGGTACTGTACTAGC.