Question

If the sequence of Nitrogenous bases in one strand of DNA-helix is 5'-ATGCATGCATGCATGC-3' then what will be the sequence of nitrogenous bases in the complementary strand of that DNA helix in 3' $\to$ 5' direction?

Hint:

When working with DNA sequences, remember that adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). The complementary strand is always read in the 3' to 5' direction.

Answer 1

Base Pairing in DNA:
In DNA, the two strands are complementary to each other, meaning that the nitrogenous bases on one strand pair with complementary bases on the opposite strand. The base pairing rules are as follows: - Adenine (A) pairs with Thymine (T)
- Thymine (T) pairs with Adenine (A)
- Cytosine (C) pairs with Guanine (G)
- Guanine (G) pairs with Cytosine (C)
###

Step 1: Understanding the given DNA sequence The given sequence of one strand of DNA is: \[ 5'-\text{ATGCATGCATGCATGC}-3' \] ###

Step 2: Writing the complementary bases Now, we need to find the complementary bases for each nucleotide in the sequence. Applying the base pairing rules, we get: \[ 5'-A \, \text{pairs with T}, T \, \text{pairs with A}, G \, \text{pairs with C}, C \, \text{pairs with G} \] ###

Step 3: Complementary sequence in the 3' to 5' direction Starting from the left end (5') of the given strand, the complementary sequence will be formed as follows: - 5'-A \underline{T}-3'
- 5'-T \underline{A}-3'
- 5'-G \underline{C}-3'
- 5'-C \underline{G}-3'
- 5'-A \underline{T}-3'
- 5'-T \underline{A}-3'
- 5'-G \underline{C}-3'
- 5'-C \underline{G}-3'
- 5'-A \underline{T}-3'
- 5'-T \underline{A}-3'
- 5'-G \underline{C}-3'
- 5'-C \underline{G}-3'
Thus, the complementary sequence in the 3' $\to$ 5' direction will be: \[ 3'-\text{TACGTACGTACGTACG}-5' \] ###

Step 4: Final answer The sequence of nitrogenous bases in the complementary strand in the 3' $\to$ 5' direction is: \[ \boxed{3'-TACGTACGTACGTACG-5'} \]