Question

Actual gels don't have labels. Here, the labels have been removed, but the ladder remains the same as in the previous example. 6. On the gel to the right, write the approximate size of each DNA fragment. Write the sizes next to each appropriate band. 7. Imagine that you have a sample of DNA that contains a single, specific DNA sequence. Before you run your gel, you split your sample into two tubes. You run the DNA from the first tube in lane two of your gel. You take the other tube and use an enzyme called a restriction enzyme that cuts the DNA into two pieces at a specific point in the sequence. You then run this sample that was cut on the gel. IEEE Which of the next three lanes (lane 3, 4, or 5) could be the same sample from lane two after it was cut into two pieces?

Answer 1

6.Here, from the gel results, Lane 1 refers to DNA marker/ ladder. In this gel 100 bp ladder has been used. The appropriate sizes of the band is as given below:

LANEI: MARKER SAMPLE DNA ILANE 2 LANE 3: LANE 4 LANE 5 da 1517 - 1200+ 1000+ 890 bp 900 da oot 620 bp 500 + 460 bp 4004 300€ 230 bp 240 bp doot 1007 Jg as

7. Answer is: Lane 4, contains the same sample DNA from lane 2 after it was cut into two pieces.

The reason is:

Lane 2 DNA shows band at 700 bp , and when it has been digested with a restriction enzyme , which cuts at a specific site obviously produces two fragments. The length of these two fragments when summed up together should produce the length of the original DNA as in lane 2 (700 bp).

Lane 3,4 and 5 produces two fragments , hence the resstion digestion/ cut is at only single point leading to two fragments. Hence,

Lane 3:  230 bp + 620 bp = 850 bp

Lane 4: 240 bp+ 460 bp= 700 bp

Lane 5: 50 bp + 890 bp = 940 bp.

Hence lane 4 contains the same sample DNA from lane 2.