High DNA Mass Ladder

Sequences of Invitrogen DNA and RNA ladders are proprietary.

Invitrogen DNA ladders contain linear dsDNA fragments.

Invitrogen DNA ladders are composed of double-stranded DNA fragments only.

Here are a few reasons why you might see smearing of the bands:

- The DNA was degraded. Avoid nuclease contamination of DNA standards.
- Too much DNA was loaded on the gel. Decrease the amount of DNA in the gel.
- The DNA was contaminated by protein. Remove proteins by phenol extraction before electrophoresis.
- For small DNA, the bands may have diffused during staining. Add the ethidium bromide before electrophoresis.
- For radiolabeled DNA, labeling was performed by nick translation. Label the DNA by replacement synthesis with T4 DNA polymerase or label the 5' end with T4 polynucleotide kinase.
- Improper electrophoresis conditions were used. Do not allow voltage to exceed ~20 V/cm. Maintain a temperature <30°C during electrophoresis. Check that the electrophoresis buffer used has sufficient buffering capacity.
- The DNA contained too much salt. Remove excess salt by ethanol precipitation before electrophoresis.

This can happen if the marker was heated. Please ensure that the ladders are not heated before use.