Explain4 marksStandard
A student performed PCR to amplify a 1400 bp gene from a bacterial genome. The PCR product was then digested with the restriction endonuclease EcoRI, which cuts the amplified gene at a single recognition site, producing two fragments. The digested sample was loaded onto an agarose gel alongside a DNA ladder containing fragments of known sizes. After electrophoresis, the distance each fragment migrated from the well was measured. The results are shown in the table.
| Fragment source | Distance migrated (cm) | Fragment size (bp) |
|---|---|---|
| Ladder | 6.0 | 200 |
| Ladder | 5.0 | 400 |
| Ladder | 4.2 | 600 |
| Ladder | 3.6 | 800 |
| Ladder | 3.0 | 1000 |
| Ladder | 2.5 | 1400 |
| Digested PCR product (band 1) | 4.2 | ? |
| Digested PCR product (band 2) | 3.6 | ? |
Explain how gel electrophoresis separates the two digested fragments, and determine the sizes of the fragments using the data in the table.