Science Buddies: "Ask an Expert"

Hello,
I'm supposed to do this project for biology on the ionizing radiation on yeast. I'm having a hard time coming up with how to go about my hypothesis and conclusion to it. I want them to make sense and to go along with each other of course. I have 3 groups of yeast starters that I have mixed with filtered water at a 1:1 ratio. a control group, low dose, and high dose group. I think the easier thing to look for is the metabolic activity. But how do I go about measuring how active they are and putting it into words? Please help

Thank you

Hi persiasef -

There are a number of resources on this site that explain how to formulate a hypothesis. It's not really that hard - think about what you expect to have happened to the yeast cells that have received different levels of x-rays, and then put it into very specific words. After you did your experiments and looked at the data, you want to be able to go back to that initial statement, point at your numbers, and be able to say something along the lines of "Yes, according to this number, it did" or "No, it didn't".

For metabolic activity, you could resuspend the 3 different yeast batches in growth medium without access to oxygen from the air and then measure the amount of carbon dioxide they produce in a fixed amount of time, or over time. You could also measure the disappearance glucose in the medium with indicator sticks made to measure the glucose levels in the urine of diabetics.

An alternative option you have is looking at the number of viable cells. Depending on the x-ray dose, a large number of yeast cells might not be viable anymore. You could plate the cells on a suitable yeast medium plate and count how many colonies you get. You probably would have to do a dilution series - you don't want to have more than about 100 colonies per plate, and it is hard to predict at what dilution you will get that number.