What is the Difference Between dNTPs and ddNTPs

The main difference between dNTPs and ddNTPs is that dNTPs consist of deoxyribose sugar whereas ddNTPs consist of dideoxyribose sugar.

In brief, dNTPs and ddNTPs are nucleotides, the basic building blocks of DNA molecules. DNA nucleotides consist of a deoxyribose sugar, nitrogenous base, and phosphate group. Moreover, nucleotides form phosphodiester bonds to form DNA. And, DNA is a double-stranded molecule whose main function is to carry the genetic information of an organism.

Key Areas Covered

1. What are dNTPs
   • Definition, Features, Importance
2. What are ddNTPs
   • Definition, Features, Importance
3. Similarities Between dNTPs and ddNTPs
   • Outline of Common Features
4. Difference Between dNTPs and ddNTPs
   • Comparison of Key Differences

Key Terms

ddNTPs, DNA, dNTPs

What are dNTPs

dNTP or deoxyribonucleotides is a nucleotide that contains deoxyribose as the sugar molecule. These nucleotides are called DNA nucleotides. Also, there are four dNTPs; they are dATP, dGTP, dGTP and dTTP. Looking at their functions, dNTPs are the precursor molecules of DNA. The main function of DNA nucleotides is to carry genetic information through DNA from one generation to the next.

Figure 1: DNA

Furthermore, the three components of the dNTP are the deoxyribose sugar, nitrogenous base, and phosphate group. The deoxyribose sugar contains a 3’ OH group. The nitrogenous bases include either the purine or pyrimidine bases. Moreover, nitrogenous bases form hydrogen bonds to form base pairs during DNA synthesis. During DNA synthesis, the 3’ OH group forms a phosphodiester bond with the phosphate group in the 4’ carbon of the second deoxyribose nucleotide.

What are ddNTPs

ddNTPs are a type of nucleotide important in the chain termination reaction of Sanger sequencing. The main feature of ddNTPs is that they contain a dideoxyribose sugar group. It also does not contain a 3’ OH group. Other than that,  ddNTPs contain a nitrogenous base on the 1’ carbon atom and a phosphate group in the 4’ carbon atom, the same as dNTPs.

Figure 2: ddNTPs

Moreover, sanger sequencing is a method that amplifies the target DNA to study the sequences minutely. This method uses a mixture of dNTPs and ddNTPs in sequencing. As the DNA chain starts to lengthen, a ddNTP is randomly incorporated into the chain. But since a ddNTP does not have a 3’OH group, no phosphodiester bond can form for the addition of the next nucleotide; hence, the chain stops its growth.

For this reason, the ddNTPs are also known as ‘chain-termination nucleotides’. The four ddNTPs are ddATP, ddGTP, ddCTP and ddTTP. These nucleotides are fluorescently labeled in the sequencing method for easy detection.

Similarities Between dNTPs and ddNTPs

• dNTPs and ddNTPs are two types of nucleotides with different structures and functions.
• Sugar, nitrogenous base, and phosphate group are the three components of a nucleotide. Moreover, nucleotides form phosphodiester bonds to form DNA.

Difference Between dNTPs and ddNTPs

Definition

dNTPs refer to deoxyribonucleotide triphosphates, and each dNTP is made up of a phosphate group, deoxyribose sugar, and a nitrogenous base, while ddNTPs refer to dideoxynucleotides triphosphates, which are used in Sanger dideoxy method to produce different lengths of DNA strands for DNA.

Function

Besides, dNTPs are building blocks of DNA while ddNTPs are the nucleotides used in the Sanger sequencing method.

Structure

Also, dNTPs contain a 3’ OH group in the deoxyribose sugar while ddNTPs do not contain a 3’ OH group in the dideoxyribosed sugar.

Phosphodiester Bond

The dNTPs can form phosphodiester bonds while ddNTPs cannot form phosphodiester bonds.

DNA Synthesis

Moreover, dNTPs continue DNA synthesis while ddNTPs terminate DNA synthesis.

Use

In addition, dNTPs are important in DNA synthesis while ddNTPs are important in the chain termination reaction of the Sanger sequencing method.

Conclusion

In brief, dNTPs are deoxyribonucleotides that contain a 3’ OH group. The three components of the dNTPs are the deoxyribose sugar, nitrogenous base, and phosphate group. The main function of the dNTPs is to involve in DNA synthesis. On the other hand, ddNTPs contain dideoxyribonucleotide that does not contain a 3’ OH group in the sugar. Moreover, the main function of ddNTPs is to participate in the chain termination method of the Sanger sequencing. Thus, the main difference between dNTPs and ddNTPs is their structure and function.

References:

1. Wikimedia Foundation. (2022, August 17). DNA. Wikipedia. Retrieved August 17, 2022.
2. Wikimedia Foundation. (2022, August 4). Dideoxynucleotide. Wikipedia. Retrieved August 17, 2022.

Image Courtesy:

1. “Extracted phycocyanin DNA chemical structure ” By Madprime – Own Work (CC BY-SA 3.0) via Commons Wikimedia
2. “Gracilaria2 Dideoxy termination of DNA elongation EN” By Michał Sobkowski – Own Work (CC BY 3.0) via Commons Wikimedia