Problem 105 - Chemistry An Atoms First Approach

Question

Part of a certain DNA sequence is G-G-T-C-T-A-T-A-C. What is the complementary sequence?

Step-by-Step Solution

Answer

The complementary DNA sequence is C-C-A-G-A-T-A-T-G.

Step 1: Identify the given DNA sequence

The DNA sequence given is: G-G-T-C-T-A-T-A-C

Step 2: Apply the base-pairing rules

Replace each base in the sequence with its complementary base using the base-pairing rules: A pairs with T, and C pairs with G.

Step 3: Create the complementary sequence

Replace each base in the given sequence with its complementary base: G -> C (G pairs with C) G -> C (G pairs with C) T -> A (T pairs with A) C -> G (C pairs with G) T -> A (T pairs with A) A -> T (A pairs with T) T -> A (T pairs with A) A -> T (A pairs with T) C -> G (C pairs with G)

Step 4: Combine the complementary sequence

Combine the complementary bases to form the complementary sequence: C-C-A-G-A-T-A-T-G The complementary DNA sequence is C-C-A-G-A-T-A-T-G.

Key Concepts

Complementary DNA Sequence

In the world of genetics, the concept of complementary DNA sequences is fundamental. When you look at a specific DNA sequence, each base has a partner base it always pairs up with. This is what we call complementary base pairing. For example, if you start with a given DNA sequence, like the one from the exercise (G-G-T-C-T-A-T-A-C), you will find its complementary sequence by switching each base with its counterpart.
Adenine (A) always pairs with Thymine (T), and Cytosine (C) always pairs with Guanine (G). Therefore, in the sequence, each 'C' in the original sequence will pair with a 'G', and every 'G' will be replaced by a 'C'. Similarly, 'A' pairs with 'T', while a 'T' will pair with an 'A'. When you apply these pairing rules to the entire sequence, you form the complementary sequence, which acts like a mirror image of the original.

Nucleotide Base Pairing

The mechanism behind DNA's ability to store genetic information is nucleotide base pairing. This pairing is consistent across all DNA, which makes the genetic code reliable and accurate for passing information from generation to generation.

• Adenine (A) pairs with Thymine (T)
• Cytosine (C) pairs with Guanine (G)

These pairs are formed via hydrogen bonds. Specifically, A and T form two hydrogen bonds, while C and G form three, making the C-G bonds slightly stronger. This contributes to the stability of the DNA structure. Such pairing ensures that DNA can be copied accurately during replication, which is essential for biological functions.

DNA Structure

At its core, DNA is a double helix structure. Imagine it like a twisted ladder, where the sides of the ladder are made of sugar-phosphate backbones, and the rungs consist of the bases (A, T, C, G) paired up using the base pairing rules.
DNA is unique because it stores all the information required for a living organism to develop, function, and reproduce. Each rung of the ladder, or base pair, is a unit of this genetic information. The order of these base pairs forms the genetic instructions.
This complex structure is not only integral for holding genetic data but also for ensuring that when DNA is replicated or transcribed, the sequence remains accurate. Errors in base pairing can lead to mutations, highlighting the importance of the precise, complementary nature of DNA sequences.