Consider the following segment of DNA:
       5'-...ATGCCAGTCACTGACTTG...-3'
       3'-...TACGGTCAGTGACTGAAC...-5'

How many hydrogen bonds are present in this DNA segment?

Key Concepts

Base Pairing in DNA

DNA consists of two strands that are held together by hydrogen bonds between complementary nitrogenous bases. Adenine (A) pairs with Thymine (T) through two hydrogen bonds, while Guanine (G) pairs with Cytosine (C) through three hydrogen bonds. Understanding this base pairing is essential for calculating the total number of hydrogen bonds in a given DNA segment.

DNA Structure

DNA has a double helix structure, where two strands run in opposite directions (antiparallel). Each strand is composed of a sugar-phosphate backbone and nitrogenous bases. Recognizing the orientation of the strands is crucial for identifying which bases are paired and thus determining the number of hydrogen bonds formed between them.

Counting Hydrogen Bonds

To find the total number of hydrogen bonds in a DNA segment, one must identify the base pairs and apply the specific number of hydrogen bonds associated with each pair. For example, each A-T pair contributes two hydrogen bonds, while each G-C pair contributes three. This counting process is fundamental to answering the question accurately.