Lab 9

Question 1

colchicine and cycloheximide.

Answer 1

Colchicine binds to free tubulin dimers and prevents the addition of dimers to microtubules.
Cycloheximide is a potent inhibitor of protein synthesis.

Question 2

Deflagellate the algae in the beaker by

Answer 2

rapidly lowering the pH of the medium

Question 3

Flagella are

Answer 3

extensions from the cell surface that consist of 9 doublets of microtubules, 2 central microtubules, plus several MAPs

Question 4

Discuss, in a few sentences, how cycloheximide and colchicine affect flagellar regeneration

Answer 4

Cycloheximide is a potent inhibitor of protein synthesis so it acts to stop the entire process of micro tubular formation. As soon as it’s added flagella stop growing, so the only thing left in the solution is whatever managed to grow before cycloheximide was added. This means that flagella cannot at all regenerate in the presents of cycloheximide. Colchicine binds to free tubulin dimers and prevents the addition of dimers to microtubules. This means that the formation of microtubules are halted until the 5mls of of colchicine is used up by binding to the dimers, after that the dimers that are still being formed start making more microtubules again. Therefore the process of microtubule formation is briefly halted till colchicine is used then continues.

Question 5

What was the purpose of collecting flagellar-length measurements for the original culture (non-deflagellated cells)?

Answer 5

added mainly to prove that the lugs iodine and medium I did not cause deflagration but rather the acid added caused deflagration

Question 6

Before measuring flagellar length in the microscope, you had to place a few drops of the culture into a tube containing Medium I and Lugol’s iodine. What was the purpose of this step? (1 MARK) (Hint: What did the Lugol’s do to the algal cells and how was this helpful?)

Answer 6

The purpose of adding the culture into a tube with Medium I and Lugol’s iodine is to freeze the process of flagella formation and also to stain the cells so that they can be easily viewed under the microscope. By freezing the flagella formation (kill the cells) , there’s no time constraint that the experiment must be performed under so the experiment could accurately be performed knowing that flagella length was being measure at the precise time it needed to be.