Genetics Staining Lab 3 2021/2022 PDF

# Genetics (B252) 2021/2022 Lab 3 ## Stains - Stain: is a substance that adheres to a cell, giving the cell color. - The presence of color gives the cells significant contrast so they are much more visible. - Stain of synthetic nature are called dye. - Those extracted from animals or plants are k...

# Genetics (B252) 2021/2022 Lab 3 ## Stains - Stain: is a substance that adheres to a cell, giving the cell color. - The presence of color gives the cells significant contrast so they are much more visible. - Stain of synthetic nature are called dye. - Those extracted from animals or plants are known as pigment. ## Staining Technique Staining is a technique used in microscopy to enhance contrast in the microscopic image. ## Classification of Stains ### According to Origin | Origin | Example | |---|---| | Animal | Carmine (form body insect) | | Plant | Hematoxylin (from Mexican tree) | | Synthetic | Eosin | ### According to Mode of Action | Mode of Action | Example | |---|---| | Physical staining | Sudan III (orange-yellow color) | | Chemical staining | Chemically reacted with structure | #### Physical Staining - The stain is physically combined with its corresponding structure (by absorption). - Sudan III: a physical stain consisting of a powder usually dissolved in alcohol, but it is soluble in fats. - Therefore, when it comes near fats. It leaves the alcohol to be dissolved in fats giving rise to an orange-yellow color. #### Chemical Staining According to the color of inducing radical. - Acid Stains: color is given by the acid radical (e.g. Eosin) - Basic stain: the color is given by the basic radical (e.g. basic fuchsin, hematoxylin). - Neutral Stains: the color is given by both basic and acid radical (e.g. staining blood cells) - Substances having the affinity for acid stains are known as acidophilic (alkaline cytoplasm). - Substances having the affinity for basic stains are called basophilic (e.g. DNA). ### According to End Color of Stained Content | Content | Example | |---|---| | Orthochromatic Stains | Cytoplasm with M.B. gives blue | | Metachromatic Stains | Starch with 12 gives blue | - Metachromasia: the reaction between the stain and the content results in a color different from that of the stain itself. ## Classification of Staining Techniques ### According to Number of Used Stains | Dye | Example | |---|---| | Monochromatic (simple) staining | One dye is used | | Polychromatic staining | Many dyes are used. Accordingly, different structures become stained in different colors | #### Polychromatic Staining - Staining in succession: the stains are used one after the other. - Staining by a mixture of dyes: the staining takes place at the same time. (e.g. the trichrome stain involves three types of stains) ### According to Nature of Stained Material | Method | Example | |---|---| | Staining in toto | The staining of the entire mass of the tissue | | Section staining | The specimen is firstly sectioned and then sections are stained | | Vital Staining | Vital stains are those which can diffuse through the living (or fresh) tissues and stain them with no harmful effects. Therefore, they must be "Non-toxic." | #### Vital Staining - Intravital Stains: these can stain living cells inside the living body (i.e. in vivo). - Supravital Stains: these can stain living (or fresh) cells outside the body (i.e. in vitro). ### According to Applied Method | Method | Example | |---|---| | Regressive (Retrogressive) Method | Over staining of sections was firstly applied then followed by removal of excess stain until the desired intensity is reached. (e.g. staining by crystal violet in paraffin technique) | | Progressive Method | Sections are stained gradually until they reach the right intensity. (e.g. staining by basic fuchsin in Feulgen technique) | | Staining through the use of a Mordant | Treatment of the tissue with a special mordant is needed to allow the color of the stain to be more fixed to this tissue. (e.g. iodine solution for crystal violet in bacterial Gram staining and paraffin technique) | | Special Methods | As those applied for some types of microscopy (e.g. fluorescent and electron microscopy) |