if one chain of a DNA molecule has the base order 5'ATTGACGT3' . . . . . Then the base order of its complementary chain will be

Options

A. 3'ATTGACGT 5'
B. 5'TGCAGTTA 3'
C. 5'TUUCTGCU 3'
D. 3' TAACTGCA 5'

Answer

To determine the base order of the complementary DNA chain for the given sequence 5' ATTGACGT 3', we will follow these steps:

### Step-by-Step Solution:

1. **Identify the Given Sequence**:
The sequence provided is 5' ATTGACGT 3'.

2. **Understand Base Pairing Rules**:
In DNA, 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)

3. **Write the Complementary Bases**:
We will now write the complementary bases for each base in the given sequence:
- A (from ATTGACGT) pairs with T
- T pairs with A
- T pairs with A
- G pairs with C
- A pairs with T
- C pairs with G
- G pairs with C
- T pairs with A

4. **Construct the Complementary Sequence**:
Now, we will write down the complementary bases in the same order:
- The complementary bases are: T, A, A, C, T, G, C, A.

5. **Determine the Direction**:
Since the original strand is given in the 5' to 3' direction, the complementary strand will be in the 3' to 5' direction. Thus, we write the complementary sequence as:
3' T A A C T G C A 5'.

6. **Final Answer**:
Therefore, the base order of the complementary chain is:
3' T A A C T G C A 5'.