For the following fragment of DNA, determine the number of hydrogen bonds and the number of phosphodiester bonds present:
5'-ACGTAGAGTGCTC-3'
3'-TGCATCTCACGAG-5'

Verified step by step guidance

1. Step 1: Understand the structure of DNA. DNA is composed of two strands that are complementary and antiparallel. Each base pair is connected by hydrogen bonds, and the backbone of each strand is connected by phosphodiester bonds.
2. Step 2: Count the hydrogen bonds between the base pairs. Adenine (A) pairs with Thymine (T) via 2 hydrogen bonds, and Cytosine (C) pairs with Guanine (G) via 3 hydrogen bonds. Analyze the sequence to determine the number of each base pair and calculate the total hydrogen bonds.
3. Step 3: Count the phosphodiester bonds in the DNA backbone. Phosphodiester bonds connect the sugar-phosphate backbone of each strand. For a single strand of DNA, the number of phosphodiester bonds is one less than the number of nucleotides. Count the nucleotides in one strand and subtract 1 to find the number of phosphodiester bonds in that strand.
4. Step 4: Multiply the phosphodiester bond count by 2 since there are two strands in the DNA molecule. This gives the total number of phosphodiester bonds in the double-stranded DNA.
5. Step 5: Combine the results from steps 2 and 4 to summarize the total number of hydrogen bonds and phosphodiester bonds present in the given DNA fragment.

Key Concepts

Hydrogen Bonds

Hydrogen bonds are weak interactions that occur between complementary nitrogenous bases in DNA. In the double helix structure, adenine (A) pairs with thymine (T) through two hydrogen bonds, while cytosine (C) pairs with guanine (G) through three hydrogen bonds. Understanding the number of hydrogen bonds is crucial for determining the stability and structure of the DNA molecule.

Phosphodiester Bonds

Phosphodiester bonds are covalent linkages that connect the sugar and phosphate groups of adjacent nucleotides in a DNA strand. These bonds form the backbone of the DNA molecule, providing structural integrity. Each DNA strand has a continuous chain of phosphodiester bonds, and recognizing their presence is essential for understanding the overall structure and function of DNA.

Complementary Base Pairing

Complementary base pairing refers to the specific pairing of nitrogenous bases in DNA, where A pairs with T and C pairs with G. This principle is fundamental to DNA replication and transcription, as it ensures accurate copying of genetic information. Identifying the base pairs in the given DNA sequence is necessary to calculate the number of hydrogen bonds formed between the strands.