The following figure (Figure 1.6) presents simplified depictions of nucleotides containing deoxyribose, a nucleotide base, and a phosphate group. Use this simplified method of representation to illustrate the sequence 3'-AGTCGAT-5' and its complementary partner in a DNA duplex.

How many hydrogen bonds are present in this DNA duplex?

Verified step by step guidance

1. Step 1: Understand the structure of DNA. DNA is a double-stranded molecule where each strand is composed of nucleotides. Each nucleotide consists of three components: a deoxyribose sugar, a phosphate group, and a nitrogenous base (adenine (A), thymine (T), guanine (G), or cytosine (C)). The two strands are complementary and antiparallel, meaning one strand runs 5' to 3' while the other runs 3' to 5'.
2. Step 2: Write the given sequence 3'-AGTCGAT-5' in the correct orientation. Since the sequence is provided in the 3' to 5' direction, you can directly use it as the template strand.
3. Step 3: Determine the complementary strand. Use the base-pairing rules: adenine (A) pairs with thymine (T) via two hydrogen bonds, and guanine (G) pairs with cytosine (C) via three hydrogen bonds. Write the complementary strand in the 5' to 3' direction, ensuring the antiparallel orientation.
4. Step 4: Count the hydrogen bonds. For each A-T pair, there are 2 hydrogen bonds, and for each G-C pair, there are 3 hydrogen bonds. Identify the number of A-T and G-C pairs in the sequence and calculate the total number of hydrogen bonds.
5. Step 5: Verify your work. Double-check the complementary strand for correct base pairing and antiparallel orientation. Ensure the total hydrogen bond count matches the number of base pairs in the DNA duplex.

Key Concepts

Nucleotides

Nucleotides are the building blocks of DNA and RNA, consisting of three components: a sugar (deoxyribose in DNA), a phosphate group, and a nitrogenous base. The sequence of these bases encodes genetic information. In DNA, the four types of nitrogenous bases are adenine (A), thymine (T), cytosine (C), and guanine (G). Understanding the structure of nucleotides is essential for analyzing DNA sequences.

Complementary Base Pairing

In DNA, complementary base pairing refers to the specific pairing of nitrogenous bases across the two strands of the double helix. Adenine pairs with thymine (A-T) through two hydrogen bonds, while cytosine pairs with guanine (C-G) through three hydrogen bonds. This pairing is crucial for the stability of the DNA structure and for accurate DNA replication and transcription.

Hydrogen Bonds in DNA

Hydrogen bonds are weak interactions that occur between the nitrogenous bases of the two DNA strands, contributing to the overall stability of the DNA double helix. Each A-T pair forms two hydrogen bonds, while each C-G pair forms three. The total number of hydrogen bonds in a DNA duplex can be calculated by analyzing the base pairs in the given sequence and their complements.