Introduction to Markers and Ladders

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 Introduction

Sigma-Aldrich offers a variety of markers that aid size determination of samples separated by agarose and/or polyacrylamide gel electrophoresis. These products include markers for DNA, PCR fragments and RNA and can be concurrently run with the samples. All the markers stain well with common nucleic acid stains. For more information on selecting appropriate markers, please visit the Markers and Ladders Selection Guide.

 Standard DNA Markers

Standard DNA markers are generated by restriction digestion of plasmid and deproteinization of the DNA fragments. The molecular weight of the digested DNA fragments determines the distance they would migrate on the gel. The standard DNA markers are useful in size determination of dsDNA as well as PCR-generated DNA fragments.

The 1 kb DNA Ladder is particularly popular as it can be used to determine the size of most medium-sized plasmids and DNA fragments. The marker is suitable for normal size gels, where DNA fragments will separate within a relatively short distance.

Sigma-Aldrich offers the following standard DNA markers:

Catalog Number

Name

 

Recommended Gel Type
Ready-to-use
Recommended load volume
Number of loads per vial
D3812 DirectLoad™ 50 bp DNA Step Ladder Agarose (2.0%), polyacrylamide Yes 10 µL 100
S7025 50 bp DNA Step Ladder Agarose (2.0%), polyacrylamide No* 10 µL 100
D7058 DirectLoad™
Wide Range DNA Marker
Agarose (0.75-2.0%), polyacrylamide Yes 10 µL 100
D5042 123 bp DNA Ladder Agarose (1.5%), polyacrylamide No* 10 µL 100, 250
D3937 DirectLoad™ 1 kb DNA Ladder Agarose (0.75%), polyacrylamide Yes 5 µL 100
D0428 1 kb DNA Ladder Agarose (0.75%), polyacrylamide No* 5 µL 100

 

*The markers should be diluted in gel loading buffer before loading in a lane of agarose or polyacrylamide gel

 Digested DNA Markers

Digested DNA markers are generated by the digestion of plasmid by specific restriction enzyme. These markers are useful in size determination of digested DNA fragments.

Sigma-Aldrich offers the following digested DNA markers: 

Catalog Number

Name

 

Recommended Gel Type
Ready-to-use
Recommended load volume
Number of loads per vial
D9655 pBR322 Hae III Digest Agarose (2.5%), polyacrylamide Yes 10 µL 200, 1,000
D0672 ΦX174 DNA Marker Hae III Digest Agarose (2.0%), polyacrylamide No* 5 µL 40, 200
D6293 pUC18 DNA Hae III Digest Agarose (2.5%), polyacrylamide Yes 3 µL 40, 200
D9780 Lambda DNA Hind III Digest Agarose (0.75%), polyacrylamide No* 10 µL 20, 100, 500, 1,000
D9281 Lambda DNA EcoR I Hind III Digest Agarose (0.7%), polyacrylamide Yes 10 µL 100, 500
D2916 Lambda DNA Mixed Digest Agarose (0.75%), polyacrylamide No* 6 µL 10, 50

 

* The markers should be diluted in gel loading buffer before loading in a lane of agarose or polyacrylamide gel.

 PCR Markers

These markers contain smaller DNA fragments that are useful in size determination of PCR fragments.

Sigma-Aldrich offers the following PCR markers:

 

Catalog Number

Name

 

Recommended Gel Type
Ready-to-use
Recommended load volume
Number of loads per vial
P1598 PCR 20 bp Low Ladder Agarose (2.5%) No* 5 µL 80
D3687 DirectLoad™
PCR 100 bp Low Ladder
Agarose (2.0%), polyacrylamide Yes 5 µL 75
P1473 PCR 100 bp Low Ladder Agarose (2.0%) No* 2 µL 75
P9577 PCR 50 - 2,000 bp Marker Agarose (2.0%), polyacrylamide Yes 5 µL 50

 

*The markers should be diluted in gel loading buffer before loading in a lane of agarose or polyacrylamide gel.

DirectLoad™ is a trademark of Sigma-Aldrich Co. LLC