Question

Which is the complementary mRNA strand from the following DNA template? TTC AGC

A: CCU GAU

B: CCT GAT

C: AAG TCG

D: AAG UCG

Answer 1

To determine the complementary mRNA strand from the DNA template "TTC AGC", we need to follow these steps:

1. **Identify the DNA template strand**: The given DNA strand is "TTC AGC".
2. **Determine the complementary DNA strand**: The base pairing rules for DNA are:
- Adenine (A) pairs with Thymine (T)
- Thymine (T) pairs with Adenine (A)
- Cytosine (C) pairs with Guanine (G)
- Guanine (G) pairs with Cytosine (C)

Therefore, the complementary DNA strand for "TTC AGC" would be "AAG TCG".

3. **Transcribe the complementary DNA into mRNA**: In RNA, the base pair rules change slightly:
- Adenine (A) pairs with Uracil (U)
- Thymine (T) is replaced by Adenine (A)
- Cytosine (C) pairs with Guanine (G)
- Guanine (G) pairs with Cytosine (C)

The complementary DNA strand "AAG TCG" translates to mRNA as follows:
- A → U
- A → U
- G → C
- T → A
- C → G
- G → C

So, the mRNA sequence will be "UUC AGC".

However, we want to check our provided options against the conversion of the DNA template directly to mRNA:

**From the original DNA template "TTC AGC":**
- T → A
- T → A
- C → G
- A → U
- G → C
- C → G

Thus, the final mRNA strand derived directly from "TTC AGC" is "AAG UCG".

Now, looking at the options you provided:
- **A: CCU GAU** - Incorrect
- **B: CCT GAT** - Incorrect
- **C: AAG TCG** - This is the complementary DNA strand, not mRNA, so it’s incorrect for our question.
- **D: AAG UCG** - This is the correct mRNA complementary strand.

**The correct answer is D: AAG UCG.**