FAQ: What ends will my PCR products have?

APPLICATION

POLYMERASE PRODUCTS

PCR PRODUCT ENDS

High fidelity PCR

Q5® polymerases

Blunt

Phusion® polymerases

Blunt

Routine & Specialty PCR

OneTaq® polymerases

3'A/blunt

Taq polymerases

3'A

LongAmp® polymerases

3'A/blunt

Hemo KlenTaq Polymerase

3'A

Isothermal amplification

Bst polymerases

3'A

Bsu Polymerase

3'A

phi29 Polymerase

Blunt

DNA manipulation

T7 DNA Polymerase

Blunt

E. coli DNA Polymerase I

Blunt

DNA Polymerase I, Large (Klenow) Fragment

Blunt

Klenow Fragment (3′-5′ exo-)

3'A

T4 DNA Polymerase

Blunt


Vent® Polymerase

Blunt

Vent® (exo-) Polymerase

3'A

Deep Vent® Polymerase

Blunt

Deep Vent® (exo-) Polymerase

3'A

 

For more details about our polymerases, including exonuclease activities and applications, please visit our DNA Polymerase Selection Chart.


Learn More

For more information about exonuclease activity, check out this FAQ.

Why do some polymerases blunt and others add a nucleotide?
Polymerases that possess proofreading (3´-5´ exonuclease) activity, such as Q5, Phusion, and Deep Vent, will add an untemplated nucleotide to the 3' ends of extended DNA fragments, but the exonuclease activity subsequently removes it.
 
Other polymerases that lack 3´-5´ exonuclease activity (such as Taq and Taq-based polymerases) will add an extra nucleotide to 3´ ends (predominantly, but not exclusively, dA) and leave the untemplated overhang intact. This is why it is important to know which polymerase to use when performing blunt-end or T/A cloning.
 
OneTaq and LongAmp Taq DNA polymerases are optimized blends of Taq (a Family A polymerase) and Deep Vent (a Family B polymerase) DNA Polymerases. The intrinsic polymerase activity of Taq adds a non-templated 3´A, while the 3´–5´ exonuclease activity of Deep Vent increases the fidelity and robustness of Taq, but also blunts PCR products. This is why these products produce a mixture of DNA ends. However, the majority of ends will have a 3'A overhang.

Image comaparing overhang and blunt