If a strand of DNA has the nitrogen base sequence 5′-ATTTGC-3′, what will be the sequence of the matching strand?
The Correct Answer and Explanation is :
The sequence of the complementary DNA strand to 5′-ATTTGC-3′ is 3′-TAAACG-5′.
Explanation:
DNA consists of two strands forming a double helix, with each strand composed of nucleotides containing a sugar, a phosphate group, and a nitrogenous base. The four types of nitrogenous bases in DNA are adenine (A), thymine (T), cytosine (C), and guanine (G). These bases pair specifically: adenine pairs with thymine, and cytosine pairs with guanine, forming base pairs through hydrogen bonds.
In the given DNA sequence, 5′-ATTTGC-3′, the bases are:
- Adenine (A)
- Thymine (T)
- Thymine (T)
- Thymine (T)
- Guanine (G)
- Cytosine (C)
To determine the sequence of the complementary strand, we apply the base pairing rules:
- A pairs with T
- T pairs with A
- T pairs with A
- T pairs with A
- G pairs with C
- C pairs with G
Therefore, the complementary strand will have the sequence 3′-TAAACG-5′.
This complementary pairing ensures that the genetic information is accurately replicated during DNA replication, maintaining the integrity of the genetic code.
It’s important to note that DNA strands have directionality, indicated by the 5′ and 3′ ends. The 5′ end has a phosphate group attached to the fifth carbon of the sugar ring, while the 3′ end has a hydroxyl group attached to the third carbon. In double-stranded DNA, the strands run in opposite directions, a property known as antiparallel orientation.
Understanding base pairing and strand orientation is fundamental in molecular biology, as it underlies processes such as DNA replication, transcription, and the accurate transmission of genetic information.