The key difference between dATP and ddATP is that dATP does not terminate DNA synthesis while ddATP is able to terminate DNA synthesis. This is because ddATP has an H atom attached to 3ʹ position of the pentose sugar while dATP has an OH group attached to 3ʹ position.
dNTPs are building blocks of DNA. There are four types of dNTPs according to the purine or pyrimidine bases—dATP one of them. The nitrogenous base of dATP is adenosine. ddNTPs are nucleotides used in Sanger sequencing. There are four types of ddNTPs. ddATP is a ddNTPs.
CONTENTS
1. Overview and Key Difference
2. What is dATP
3. What is ddATP
4. Similarities Between dATP and ddATP
5. Side by Side Comparison – dATP vs ddATP in Tabular Form
6. Summary
What is dATP?
Deoxyadenosine triphosphate is a nucleotide, which is a building block of DNA. DNA polymerase enzyme uses dATP as a substrate for DNA synthesis. dATP has three components: a deoxyribose sugar molecule, an adenosine, and the three phosphate groups. Therefore, it is a purine nucleoside triphosphate. The chemical formula of dATP is C10H16N5O12P3, and its molecular mass is 491.182.
Figure 01: dATP
dATP differs from ATP (adenosine triphosphate) in terms of sugar components. ATP has ribose sugar. dATP base pairs with uracil nucleotide during transcription. In addition to participating in DNA synthesis, dATP can act as an energy-transferring molecule to maintain cell viability as well. A high level of dATP in the body is toxic since it can act as a noncompetitive inhibitor for the enzyme ribonucleotide reductase. It can lead to impaired immune function.
What is ddATP?
Dideoxyadenosine triphoaphate or ddATP is one of the four types of nucleotides used in the Sanger sequencing method. Structurally, ddATP also has three components similar to dATP. They are an adenine base, a deoxyribose sugar and three phosphates.
Figure 02: ddATP
Unlike dATP, ddATP lacks an OH group at 3ʹ position of the pentose sugar in order to form phosphodiester bond with the adjacent nucleotide and continue the chain elongation. It has an H atom in 3ʹ position. Therefore, once ddATP is incorporated, DNA synthesis comes to an end. It is the basic principle of Sanger sequencing. Therefore, ddATP works as a chain elongation inhibitor in Sanger sequencing. There are four tubes used in Sanger sequencing and ddATP is added to one tube.
What are the Similarities Between dATP and ddATP?
- dATP and ddATP are nucleotides.
- Both are composed of adenine, deoxyribose and three phosphates.
- They are organic compounds.
- Both dATP and ddATP are added into tubes in Sanger sequencing.
What is the Difference Between dATP and ddATP?
dATP has an OH group in 3ʹ position of the pentose sugar while ddATP lacks an OH group in 3ʹ position of the pentose sugar. Furthermore, dATP is a monomer used in DNA synthesis while ddATP is used to terminate chain elongation during the Sanger sequencing. So, this is the key difference between dATP and ddATP. Moreover, dATP can form phosphodiester bonds while ddATP cannot form phosphodiester bonds.
Below infographic shows more differences between dATP and ddATP in tabular form for side by side comparison.
Summary – dATP vs ddATP
In brief, dATP is a precursor to DNA synthesis while ddATP is a nucleotide used to terminate DNA synthesis in Sanger sequencing. Moreover, dATP has an OH group in 3ʹ position of pentose sugar and it allows the formation of a phosphodiester bond with the next nucleotide. Meanwhile, ddATP lacks OH group in 3ʹ position; hence, it is unable to form a phosphodiester bond with the next nucleotide. As a result, DNA sequence ceases its elongation. Thus, this summarizes the difference between dATP and ddATP.
Reference:
1. “28.6 DNA Sequencing.” Chemistry LibreTexts, Libretexts, 23 Sept. 2020, Available here.
2. “Deoxyadenosine Triphosphate.” Wikipedia, Wikimedia Foundation, 16 Dec. 2020, Available here.
Image Courtesy:
1. “Desoxyadenosintriphosphat protoniert” By NEUROtiker – Own work (Public Domain) via Commons Wikimedia
2. “DdATP” By Frederic Dardel – Own work (CC BY-SA 3.0) via Commons Wikimedia