Question

3) Image from Biotechnology Explorer Kit, BIO RAD Analysis of DNA Fragments The data you entered for the lambda Hindill digest were the relative positions of DNA bands of known size. Since the exact size and position of these fragments are known, they can be used as standard reference points to estimate the size of unknown fragment bands. A set of fragments of known sizes is called a molecular weight ruler or standards or marker (or sometimes a ladder because of the bands' appearance). Now look at the diagram of the agarose gel (below). It shows two lanes. A lane is the column below a well. The right lane contains a banding pattern from four fragments of known length (6,000, 5,000, 3,000, and 1,800 bp). Well 2000_9P Which lane contains the molecular weight standards? How do you know? The night lone because the fragment sizes are given. • Label each band in the right lane with its base-pair size 3.000bp Lyoo bp + Agarose gel Compare the two lanes of bands. Estimate the size of the fragments in the left lane. Upper band_5,000 bp Lower band 4.000 be Band 3 000 • How did you determine the sizes of the two bands in the left lane? The upper band is 5,000 because it matores the one on the right "Le louer bane s 4.000 best it's between S.000 Examine the practice gel above. Left lane Right lane Measure the distance in millimeters (mm) that each band moved. Measure from the bottom edge of the well to the bottom edge of the band. Record the data in the table to the right, including the unit of measurement, mm. IN

Answer 1

Answer: The lane on the right side of the gel contains the molecular marker or molecular weight standards. Since the right lane contains a banding pattern from four fragments of known length which is only possible if the molecular size or molecular weight of the bands are predefined such as in molecular weight rular or standards or marker which gets differentiated when run on gel.

Since the small size move faster towards the positive side as compared to long size when run on agarose gel, hence we can conclude that the upper most band is of 6000 bp as it moves slower among the other, similarly the second upper band is of 5000 bp, the third band is of 3000 bp and the last one is of 1800 bp since it has the smallest size and therefore moves faster.

By comparing the two lanes of bands we can estimate that the size of the upper band is 5000 bp and the size of the lower band is 4000 bp.

We can determine the size of the two bands by comparing them with the band size of the right lane. It is observed that the upper band of the left lane is positioned at the same distance from the well as it is found in case of 5000 bp band of right lane. Similarly, the lower band of the left lane is positioned between the 5000 bp and 3000 bp bands of the right lane which suggest that the size of the lower band is nearly equal to 4000 bp.

It is not possible to measure the distance that each band move as the distance may vary between when it is measured in worksheet and when measured it in computer screen.