Question

Write the complementary DNA base sequence for \(5^{\prime}\)-CCGTACGA-3'.

Short answer

Answer: The complementary DNA sequence for the given DNA sequence is \(5^{\prime}\)-GGCATGCT-\(3^{\prime}\).

Step-by-step solution

Identify the complementary bases

For each of the bases in the given DNA sequence, find their complementary bases according to the base pairing rules: Adenine (A) pairs with Thymine (T), and Cytosine (C) pairs with Guanine (G).

Write the complementary sequence

Using the complementary bases found in step 1, write the complementary DNA sequence for the given DNA sequence, starting at the 5' end and finishing at the 3' end. Given sequence: \(5^{\prime}\)-CCGTACGA-\(3^{\prime}\) Complementary sequence: \(5^{\prime}\)-GGCATGCT-\(3^{\prime}\)

Key concepts

DNA Base Pairing

In the world of genetics, understanding the concept of DNA base pairing is akin to learning the alphabet before constructing sentences. It's this base pairing that essentially forms the 'rungs' of the DNA double helix ladder. Each rung consists of two nucleotides paired together, following strict pairing rules: adenine (A) with thymine (T), and cytosine (C) with guanine (G).

The structure of the DNA molecule is stabilized by these partnerships, which are formed due to hydrogen bonding. A and T connect through two hydrogen bonds, while C and G are bound by three, making the C-G connection slightly stronger. As you can see, each nucleotide has its designated partner, ensuring the precise copying of genetic information during the DNA replication process.

• Adenine pairs with Thymine
• Cytosine pairs with Guanine

Nucleotide Complementarity

Nucleotide complementarity is the concept that ensures the faithful transmission of genetic information from one cell to its offspring. This concept is the foundation for both DNA replication and the less-discussed transcription processes, which are pivotal for cell division and the creation of proteins, respectively.

In the provided exercise, identifying the complementary DNA base sequence is essential. Given the original sequence, each nucleotide must be paired with its complement: C with G and G with C, A with T, and so forth. The complementary sequence mirrors the original, reflective of the base pairing rules. The resulting sequence is a literal genetic counterpart, fitting together with the original like puzzle pieces.

The Importance of Accuracy

It is crucial that this complementary process is error-free. Any mistakes in pairing could lead to mutations, which might result in a variety of functional changes within an organism. The exercise demonstrates this precision by reversing the sequence to reflect how nucleotides are arranged in opposite directions in the two DNA strands, with ends labeled as 5' and 3' denoting the direction of the sequence.

DNA Replication

DNA replication is the biological process of producing two identical replicas from one original DNA molecule. This process is extraordinarily precise and occurs within a cell's nucleus during the S phase of the cell cycle. The double helix structure unwinds and each strand serves as a template for the formation of a new companion strand.

DNA polymerases are the molecular machines that perform the replication, reading the template strand and adding complementary nucleotides. Following the base pairing rules as described earlier, they construct a new strand by matching A to T and C to G.

• Originating strand: 5'-CCGTACGA-3'
• Complementary strand formed: 5'-GGCATGCT-3'

Replication is not only about copying; it also includes proofreading and error correction. The accuracy of DNA replication ensures that each new cell has an exact copy of the DNA present in the original cell, providing it with the correct genetic instructions necessary for life.