The role of orcein in chromosome staining

[Alettix]

Hi!

So some weeks ago I did a laboration in school where we had to make or own samples of onion root cells, in order to study the different phases of mitosis in a microscope. Orcein and hydrochloric acid was used when preparing the samples, to "soften up the cells" and do dye them. My questions are:
1. Why is orcein used? How does it dye the chromosomes?
2. Why is hydrochloric acid used? How does it "soften" the cells?

Thank you!

 

[Quantum Defect]

Hi!

So some weeks ago I did a laboration in school where we had to make or own samples of onion root cells, in order to study the different phases of mitosis in a microscope. Orcein and hydrochloric acid was used when preparing the samples, to "soften up the cells" and do dye them. My questions are:
1. Why is orcein used? How does it dye the chromosomes?
2. Why is hydrochloric acid used? How does it "soften" the cells?

Thank you!

1. The dye molecules (in order to be commercially useful) must stick to something. In the early days of dye chemistry, people discovered that some dyes stuck to different biological molecules in differing ways -- basically trial and error. wikipedia has chemical structures of the orcein dye molecules. I could not find any information about how the dye binds preferentially to nuclear material, but the molecules are shaped like other molecules that interchelate inbetween stacked DNA base pairs. http://en.wikipedia.org/wiki/Orcein

2. Some sites claim that the HCl is used to soften the cell wall and separate the indiviudal plant cells. Since the cell walls of plants are made of cellulose, the HCl might simply be catalyzing the partial hydrolysis of the cellulose. see e.g. http://www.eng.umd.edu/~nsw/ench485/lab4.htm

 

[Alettix]

This was very useful! Thank you! :)