Question

During gel electrophoresis, DNA molecules can easily be separated according to size because all DNA molecules have the same charge-to-mass ratio and the same shape (long rod). Would you expect RNA molecules to behave in the same manner as DNA during gel electrophoresis? Why or why not?

Short answer

Answer: RNA molecules might not behave in the same manner as DNA during gel electrophoresis because they can have various secondary structures, resulting in different shapes and sizes that affect their migration in the gel matrix. Even though RNA and DNA have similar charge-to-mass ratios, the variation in RNA shape due to secondary structures might cause differences in their migration behavior during gel electrophoresis.

Step-by-step solution

Similarities between RNA and DNA

RNA and DNA are both nucleic acids, having a similar basic structure consisting of a sugar, a phosphate group, and a nitrogenous base. They have a similar charge and a similar charge-to-mass ratio.

Differences between RNA and DNA

DNA is double-stranded while RNA is usually single-stranded. DNA consists of deoxyribose sugar, while RNA contains ribose sugar. The nitrogenous bases in RNA include adenine, uracil, guanine, and cytosine, while DNA uses adenine, thymine, guanine, and cytosine.

Shape of RNA molecules

Unlike DNA, which has a consistent double helix structure, RNA molecules can form various secondary structures due to base-pairing interactions within the same molecule. These secondary structures can alter the shape and size of an RNA molecule.

Effect of shape and size on gel electrophoresis

During gel electrophoresis, molecules are separated based on their charge-to-mass ratio and shape. As RNA molecules can have different shapes and sizes due to their secondary structures, they can behave differently during gel electrophoresis compared to the more consistent shape of DNA molecules.

Conclusion

We would not expect RNA molecules to behave in the same manner as DNA during gel electrophoresis because RNA molecules can have various secondary structures, which can result in different shapes and sizes, affecting their migration in the gel matrix. Even though RNA and DNA have similar charge-to-mass ratios, the variation in RNA shape due to secondary structures might cause differences in their migration behavior during gel electrophoresis.