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!

"Do different color dyes have the same type of macromolecules?"

No. The fact they are different colors tells us that immediately. In addition, I would expect your data would show that the molecules migrate at different speeds through the gel.

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

Each band represents one type of molecule. If you have more than one band it means that the food coloring has more than one chemical in it. I would guess that the different bands would tend to have different colors as well. The size and charge of the molecules of each of the components will determine how far each migrates.

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

That is what you did the experiment to find out. "Yellow" food dyes from different sources could very well have different mixtures of dyes. For fun you could make your own custom food color by combining two of the commercial colorings. The pattern of bands in the gel would then have bands corresponding to both of the food colorings in your mixture.

I hope this helps. Feel free to post again if you need more help.

Thank you!

I also tested different brands of food dye. One of my brands(Great Value) only had one band for yellow and the other brand(McCormick) had two bands for yellow. Is that okay? Since the name brand probably had higher concentration of macromolecules and pigments that made up their yellow die. Right?

Also, I know that the reason for different speeds of migration through the chamber is based on the size of macromolecules. But do small or large macromolecules migrate faster?

Thanks again!

sharonholland wrote: I also tested different brands of food dye. One of my brands(Great Value) only had one band for yellow and the other brand(McCormick) had two bands for yellow. Is that okay? Since the name brand probably had higher concentration of macromolecules and pigments that made up their yellow die. Right?

That sounds reasonable to me.

sharonholland wrote: Also, I know that the reason for different speeds of migration through the chamber is based on the size of macromolecules. But do small or large macromolecules migrate faster?

Small molecules migrate faster generally speaking. The details are more complex (aren't they always ), the speed of migration also depends on the charge of the molecule, the shape of the molecule, and the distribution of the charge. Also, while I am by no means a real expert in this area, I would not call dye molecules macromolecules despite what the write-up on our site says -- I reserve the term macromolecules to molecules that are much, much larger than dye molecules. If you look up "food colorings" in Wikipedia, you can find the chemical names of several of the many food colorings in use, and if you look those up you can see what the molecules look like. They are indeed complicated compared to water, bicarbonate of sodium, salt and other simple chemicals you may be familiar with, but if you then look up "macromolecule" you can see a picture of what one of them looks like. It's the difference between a house and a city. As a scientist I have been trained to be very precise in the terms I use; I don't think you need to worry about these distinctions in your report at this stage in your career.

Glad to hear your experiment went well. Hope you do well tomorrow!

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

I'm really happy to hear that. Very exciting! Have fun.