Unit 2- Stains

Question 1

Stain used for starch?

Answer 1

Iodine as it goes black

Question 2

Stain for DNA?

Answer 2

Ethanoic orcein, stains DNA reddish purple

Question 3

Stain for nuclei or chromosomes?

Answer 3

Methylene blue

Question 4

Stain used for looking at vascular bundles

Answer 4

Phloroglucinol, which stains lignin red

Question 5

Gram staining test:

Answer 5

• add crystal violet stain to slide, (binds to peptidoglycan turning ALL bacteria purple)
• iodine assists the binding process
• add ethanol (dissolves outer lipid layer of gram negative) this washes out purple stain from gram negative but not gram positive
• add safranin (red stain) which binds to remaining peptidoglycan of gram negative