Which one of the following is the complementary sequence of 5&;TTAAGCTAC3&;?
**Core Concept**
The question is asking for the complementary sequence of a given DNA strand. In molecular biology, the complementary sequence is the sequence that pairs with the original sequence through base pairing rules (A-T and G-C). This concept is crucial in understanding DNA replication, transcription, and other genetic processes.
**Why the Correct Answer is Right**
To find the complementary sequence, we need to pair each nucleotide with its complement. The given DNA strand is 5' TTAAGCTAC 3'. Starting from the 5' end, we pair each nucleotide as follows:
- T pairs with A
- T pairs with A
- A pairs with T
- A pairs with T
- G pairs with C
- C pairs with G
- T pairs with A
- A pairs with T
- C pairs with G
Using these base pairing rules, we can determine the complementary sequence by writing the paired nucleotides in the 3' to 5' direction.
**Why Each Wrong Option is Incorrect**
**Option A:** This sequence does not follow the base pairing rules and is not the correct complement of the given DNA strand.
**Option B:** This sequence also does not follow the base pairing rules and is not the correct complement.
**Option C:** Although this sequence appears to follow the base pairing rules, it is not the correct complement of the given DNA strand, as it is missing some nucleotides.
**Clinical Pearl / High-Yield Fact**
When working with DNA sequences, remember to always check the base pairing rules (A-T and G-C) and write the paired nucleotides in the correct 3' to 5' direction to ensure accuracy.
**Correct Answer:** C. AGCTAGCTAT