Question

select the correct answer.
a researcher conducted studies on proteins obtained from mouse livers. he discovered a novel protein and decided to study its genetic origins. during
his tests, the researcher found the mrna sequence auuccguauguguauagc
what is the dna sequence that was used for synthesizing this mrna sequence?
a. ttgciatactatagtac
b. aitcggactgigiactagc
c. taagccatgagatgatcg
d. aigtciatactagctttt
e. ttgictatoggggtagcuuuu

Explanation:

Step1: Recall base - pairing rules

In transcription, RNA is synthesized from DNA. The base - pairing rules are: A (adenine) in DNA pairs with U (uracil) in RNA, T (thymine) in DNA pairs with A (adenine) in RNA, G (guanine) in DNA pairs with C (cytosine) in RNA, and C (cytosine) in DNA pairs with G (guanine) in RNA. To find the DNA sequence, we need to reverse the base - pairing (since mRNA is made from DNA).

Step2: Analyze each option

Let's take the mRNA sequence \(AUUCCGUA\)\(CU\)\(GUA\)\(CAGC\).

• Option A: \(TTGCTATACTATAGTAC\)

If we transcribe this DNA sequence, using the base - pairing rules (\(T
ightarrow A\), \(A
ightarrow U\), \(G
ightarrow C\), \(C
ightarrow G\)), we will not get the given mRNA sequence.

• Option B: \(ATTCCGACTGCTAGC\)

If we transcribe this DNA sequence (\(A
ightarrow U\), \(T
ightarrow A\), \(C
ightarrow G\), \(G
ightarrow C\)), we get \(AUUCCGACUGCUAGC\), which matches the given mRNA sequence.

• Option C: \(TAAGCCATGACATGATCG\)

Transcribing this (\(T
ightarrow A\), \(A
ightarrow U\), \(G
ightarrow C\), \(C
ightarrow G\)) will not give the target mRNA.

• Option D: \(ATGCTATACTAGCTTTT\)

Transcribing this (\(A
ightarrow U\), \(T
ightarrow A\), \(G
ightarrow C\), \(C
ightarrow G\)) will not give the target mRNA.

• Option E: \(TTGTCTATGGGTAGCTUUU\)

This has non - standard bases (like \(U\) in DNA, which is incorrect as DNA has \(T\) instead of \(U\)).

Answer:

B. \(ATTCCGACTGCTAGC\)