Plaease help me to answer these question of gel electrophres

Plaease help me to answer these question of gel electrophresis class.

Q1: What is electrophresis and why do you need to run a DNA ladder together with your sample ?

Q2 In the well where you ran pUC19 (plasmid sample with known concentration for positive contorol) , you will probably see more than one band. The purification with the silica column allows for the elimination of chromosomal contaminants, so what types of DNA molecules might be present in the different bands ( In order to ansewer this question, you need to find out how plasmids repilicate and what the properities of supercoiled plasmids are)

I can ansewer to Q1 by myself (I also asked for Q1, because I want to check my own ansewer) , but to Q2, I can\'t.

Solution

Q1: Electrophoresis is a laboratory technique used to separate macromolecules like DNA, RNA and Proteins based on size and charge.

DNA ladders are used in electrophoresis to determine the size and quantity of testing DNA fragments. Most DNA ladders will be in liquid form and a few microliters is usually loaded on to the gel. Once the samples are run in an electrophoretic unit along with the DNA ladder, the size and quantity of the testing DNA fragments can be determined by comparing with the size and quantity of the DNA bands in the DNA ladder.

Q2: The plasmid replication is strictly dependent upon the presence of specific viral sequence of DNA since pUC19 cannot replicate in the absence of viral DNA. When we run pUC19, we see more than one band in the gel. Many types of DNA molecules are present in different bands. From bottom of the gel, first we get supercoiled type of DNA molecule due to its small size and because of more foldings, it runs faster in the gel. Next, above the supercoiled form we see coiled DNA molecule, less foldings than supercoiled. On the top of coiled we see linear/ circular form of DNA molecule. Due to its large size, it runs at a very slow rate when compared to the coiled and supercoiled type of DNA molecules in the gel.