Which one of the following is the complementary sequence of 5′ TTAAGCTAC 3′ ?
**Core Concept**
The concept being tested here is the complementarity of nucleotides in DNA. Complementary DNA strands are paired in a specific manner, with adenine (A) pairing with thymine (T) and guanine (G) pairing with cytosine (C). This pairing is crucial for the replication and transcription of genetic material.
**Why the Correct Answer is Right**
To find the complementary sequence, we need to pair each nucleotide in the given sequence with its complement. The given sequence is 5' TTAAGCTAC 3'. We start from the 5' end and pair each nucleotide:
- T (5' end) pairs with A (3' end)
- 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
So, the complementary sequence is 5' AATTCGATAG 3'.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not correctly pair the nucleotides. For example, the first two nucleotides, T and A, should pair with A and T, respectively.
**Option B:** This option is incorrect because it does not correctly pair the nucleotides. For example, the first two nucleotides, T and A, should pair with A and T, respectively.
**Option D:** This option is incorrect because it does not correctly pair the nucleotides. For example, the first two nucleotides, T and A, should pair with A and T, respectively.
**Clinical Pearl / High-Yield Fact**
When finding the complementary sequence of a DNA strand, remember that adenine pairs with thymine and guanine pairs with cytosine. This pairing is crucial for the replication and transcription of genetic material.
**Correct Answer: C. 5' AATTCGATAG 3'**