Problem 1 - Biology: A Guide to the Natural World

Question

Given the following DNA sequence, determine the complementary strand that would be added in replication: $$ATTGCATGATAGCC$$

Step-by-Step Solution

Answer

The complementary DNA strand is TAACGTACTATCGG.

Step 1: Understand the Base Pairing Rules

In DNA, adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). These are the base pairing rules that you need to apply to each nucleotide in the given sequence.

Step 2: Start Building the Complementary Strand

Write down each base of the given sequence and match it with its complementary base according to the pairing rules. Begin with the first base, which is A.

Step 3: Complete the Complementary Strand

Continue matching each base with its pair: - A with T - T with A - G with C - C with G Repeat this for each base in the given sequence.

Step 4: Verify the Complementary Strand

Check that each base in the original strand has been correctly paired with its complementary base to ensure accuracy.

Step 5: Write Down the Final Complementary Sequence

Combine all the complementary bases you have determined. For the given sequence ATTGCATGATAGCC, the complementary strand will be TAACGTACTATCGG.

Key Concepts

Nucleotide Base Pairing

DNA replication is a complex process that relies heavily on the principle of nucleotide base pairing. This fundamental rule ensures that the sequence of bases on one DNA strand dictates the sequence on the newly formed complementary strand. Understanding base pairing helps us comprehend how DNA replicates itself so accurately.
Throughout DNA, specific bases pair with one another based on chemical compatibility:

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

These specific pairings are due to the number and orientation of hydrogen bonds that can form between the bases:

• Adenine and thymine form two hydrogen bonds.
• Cytosine and guanine form three hydrogen bonds.

These bonds are strong enough to hold the DNA strands together while still allowing them to separate for replication and other processes. Each pairing maintains the consistent width of the DNA double helix, contributing to the molecule's stability and efficiency in storing genetic information.

Complementary DNA Strand

A complementary DNA strand is formed during replication or transcription when the DNA base sequence is copied or read. Creating this strand involves using the original strand as a template. Each base on the template strand guides the addition of its complementary base to the forming strand.
The concept of complementary strands ensures that genetic information is accurately passed down. Whenever a cell divides, the DNA replicates, producing two complete sets of DNA: each cell receives one original strand and one newly formed complementary strand.
Key roles of complementary strands include:

• Preserving genetic information by ensuring identical DNA is produced.
• Assisting in making proteins—molecules essential for the functioning, structure, and regulation of tissues and organs in an organism.

During replication, the process starts by unwinding the DNA, breaking the hydrogen bonds between base pairs to expose the template strand for new nucleotide attachment.

Adenine-Thymine-Guanine-Cytosine

The nucleotides adenine (A), thymine (T), guanine (G), and cytosine (C) are the four building blocks of DNA. Every living organism's genetic code is constructed from various sequences of these four bases. Their specific arrangement on a DNA strand holds the key to genetic instructions used in the growth, development, functioning, and reproduction of the organism.
Here's a quick look at each:

• Adenine (A) is a purine base that pairs with thymine.
• Thymine (T) is a pyrimidine base that pairs with adenine.
• Guanine (G) is a purine base that pairs with cytosine.
• Cytosine (C) is a pyrimidine base that pairs with guanine.

The base pairing, along with the sugar-phosphate backbone, forms the structure of DNA known as the "double helix." The specific sequence of these bases along the DNA strand encodes the biological instructions that make each species unique. As DNA replicates, these sequences are copied, ensuring that new cells have the same genetic information as the parent cell.