1. Dictyostelium differentiation

2. Announcements *next two lab. sessions are Dictyostelium…. *we will meet next week to update on our experiment and take a quiz on Dicty… * The week after, there is no lab session and you should be working on the lab report (50 points) for dicty that is due in the week of November 15 th. So, find a new group to work with rather that the old one. *today there is in class prospectus (13 points) about what you will do.

3. Today *hypothesis testing *model organisms *Dictyostelium discoidium *prospectus for Dictyostelium differentiation

4. Hypothesis *hypothesis is basically an idea or a question e.g does light wavelength has any effect on Dictyostelium differentiation. *usually based on previous observations e.g the rate of dictyostelium differentiation varies *it has prediction(s) e.g certain wavelength will speed up or slow down the rate of differentiation *the researcher task is usually to test these predictions e.g grow dictyostelium in certain wavelength and compare the rate of growth to a control

5. Model organisms * It is not always easy to test hypothesis specially in biological system (or even any other type of science discipline). e.g the Moon is made up of cheese!!! * The hypothesis has to be testable. In biology, there some organisms that are easy to deal with and manipulate: E.coli D. melanogaster C. elegans D. discoidium A.thaliana

6. Dictyostelium discoidium *it is a social amoeba (unicellular eukaryotes) *its habitat is upper layer of forest soil *it is also known as slime mold *it shows sexual and asexual life cycles *adverse environmental conditions mainly starvation trigger the switch between the two life cycles. *the organism is a linkage between unicellular and multicellular life style *multicellularity is clear in the asexual cycle *cAMP is the signal of communication between cells *D.discoidium feeds on bacteria

7. Dictyostelium discoidium

8. I got the picture * choose environmental condition -temperature -light (directionality or dark -cAMP -charcoal - PH *you will be supplied with 6 nutrient agar plates with E. coli lawn in the center of the plate. one of the has to be the controle (positive)

9. I got the picture - pipette different volumes of your chemical (1-5 drops) 10  l each on the top of the disk -let the plate stand for 5 m’ *for those who chose light effect, read the protrocol in the lab manual. *for all the experiments -inoculate the center of the plate with 100  l of Dictyostelium culture. Mark this point on the plate *temperature lab room 22

10. I got the picture *what exactly am I looking for how fast slugs and fruiting bodies, with different environmental conditions, are formed. *where these things are supposed to be D. discoidium growth on agar looks like waves that are moving toward the periphery (looking for food). Where do you think the starving cells will be? * when I check my plates start Moday and do it daily till you reach the endpoint

11. I got the picture *how do I collect data set a number of microscopic field that you are going to examine and count the number of fruiting bodies and slugs and compare them across plates. *what is the homework for this week = non. However, two weeks from today a prospectus,on the hypothesis you want test and how you are going to do it, has to be turned in