A KB ladder, specifically a 1 kb DNA Ladder, is a standard reference used in molecular biology to determine the size of double-stranded DNA fragments.
Function and Use
In processes like gel electrophoresis, DNA fragments are separated based on their size. To figure out the precise size of an unknown DNA sample, scientists run a known set of DNA fragments alongside it. This known set is the DNA ladder. The 1 kb DNA Ladder serves as a ruler against which the size of your sample DNA can be measured. By comparing the migration distance of your DNA band to the bands in the ladder, you can estimate its size in base pairs (bp).
Composition of a 1 kb DNA Ladder
According to the provided reference, a 1 kb DNA Ladder allows for determining the size of double-stranded DNA from 250 to 10,000 base pairs (bp). It is composed of 13 distinct double-stranded, blunt-end fragments. These fragments have specific, known sizes, creating a ladder-like pattern when separated on a gel.
The specific fragment sizes found in this type of ladder are:
| Fragment Size (bp) |
|---|
| 250 |
| 500 |
| 750 |
| 1000 |
| 1500 |
| 2000 |
| 2500 |
| 3000 |
| 4000 |
| 5000 |
| 6000 |
| 8000 |
| 10000 |
These distinct bands make it easy to visually calibrate the size of DNA fragments run on the same gel. The "kb" in 1 kb ladder refers to kilobase pairs (1 kb = 1000 bp), indicating the approximate center or common size range covered by the ladder.
In essence, a 1 kb DNA ladder is an essential tool for accurately identifying the size of DNA fragments within the 250 to 10,000 bp range during experiments involving DNA separation.
