Science Buddies: "Ask an Expert"

I am doing the project Forensic Science: Building Your Own Tool for Identifying DNA.

I am having trouble with the data.

Do different color dyes have the same type of macromolecules?

Does number of color bands represent the number of macromolecules or the size of the marcromolecules?

Does the yellow food dye have one or two bands after going through the chamber?

Project is due March 5, 2012!

Thanks!

Hi,

Welcome to Science Buddies! I think you are doing this really great project from the Science buddies website:

https://www.sciencebuddies.org/science- ... p028.shtml

In this experiment, the molecules in food coloring are separated by gel electrophoresis. The different dyes have different structures and the number of bands represent the number of different molecules in each dye and the distance that the dyes migrated in the gel reflects the both the size and the charge of the molecule. Smaller molecules will travel faster because they can get through the pores of the agarose more quickly, and dyes that have more negative charges will migrate more quickly in the electric field.

Your project is due tomorrow, so I know you are short of time, but if you want to explain the molecular basis of your results, you could look up the structure of each dye that you used and list the molecular weight and number of charges for each molecule to confirm your results. For example, here is a website that includes the structure of Allura Red, also known as Red Dye #40. You may have used this dye if you used red food coloring. This dye has a molecular weight of 496 and it has 3 negative charges (2 sulfonic acid (SO3-) and 1 carboxyl group (COO-)

http://en.wikipedia.org/wiki/Allura_Red_AC

Brilliant blue has a molecular weight of 793 and a net negative 2 charge (3 negative sulfonic acid and one positive nitrogen group), so you would expect this molecule to migrate more slowly in the electrical field compared to Allura Red.

http://en.wikipedia.org/wiki/Brilliant_Blue_FCF

Does this make sense? Please let me know if you have more questions.


Donna Hardy

Hi,

Here is an answer for your question about yellow dye. You should look at the label of the food coloring you used and find the list of ingredients. The yellow dye may have been tartrazine, which has a molecular weight of 543 and 3 negative charges (2 sulfonic, one carboxyl). Or, it may have been a combination of two dyes. If there were two molecules used, then you should have seen two bands on your gel.

http://en.wikipedia.org/wiki/Tartrazine

Donna

do smaller or larger macromolecules migrate FARTHER? i know smaller ones go faster but what about farther?

Hi,

Good question. Smaller molecules travel faster and farther.


Donna

Just wanted to say that I won the science fair and get to go to the Regional Science Fair. Thanks for all your help!

Hi Sharon,

Congratulations on your win! I think your extra effort to understand the science behind this project really paid off. Thanks for letting us know. Good luck at the next level of competition!

Donna Hardy