Question

Which of the following is stained by using 'Leuco basic dye"?
A Bacteria
B Diatoms
C Chromosomes
D Viruses

Answer 1

Hint A leuco dye is a dye that has the ability to transition between two chemical states, one of which is colourless. Heat, light, and pH can all trigger reversible changes, resulting in thermochromism, photochromism, and halochromism, respectively.

Complete step by step answer:
Reduction or oxidation are the most common irreversible reactions. The colourless variety is referred to as the leuco variety. Thermal printer papers and certain pH indicators include leuco dyes. Sulfur dyes and vat dyes are the most prevalent examples, with indigo being a classic example. This is a typical purple colour, but it's also fully water insoluble, so it can't be directly applied to clothing. Instead, it is converted to indigo white, a water-soluble but colourless substance.
When a submerged fabric is taken from a white indigo dye bath, the dye swiftly reacts with oxygen in the air, converting the dye to the insoluble, strongly coloured indigo.
Because phosphoric acid is one of the components of nucleotides, DNA in chromosomes is an acidic molecule with a negative charge. As a result, basic dyes should be used to stain it. After staining with the dye Janus green, Waldeyer coined the word chromosomal in 1888.

So, the correct option is C.

Additional information
Another example of a leuco dye is crystal violet lactone, which is colourless or slightly yellowish in its lactone form but becomes vividly violet when protonated at low pH.

Note: Other examples are phenolphthalein and thymolphthalein, both of which are colourless in an acidic to neutral pH range but turn pink or blue in an alkaline environment. Many redox indicators, for example, undergo a reversible colour shift from colourful to colourless at a given electrode voltage.