miotic index Flashcards
miotic index=
Number of cells containing visible chromosomes ÷ Total number of cells in the field of view
risk
orcein stain can stain hands -wear gloves
scalpel is sharp and can cut -handle with care
method
1] Place a test tube of 2cm³ HCl (1moldm¯³) into a test tube rack in a 60 ̊C water bath.
2] Cut off 1-2cm of a root tip from garlic root. Put the tip in a watch glass containing 2cm³ of acetic alcohol for at least 12 minutes.
3] Remove the tip and then place into another watch glass containing 5cm³ of ice cold distilled water. Leave for 4-5 mins, and then remove and dry.
4] Place the tip into the heated HCl for 5 minutes then repeat the process again by placing tips back into acetic alcohol etc. Tip: The tips will be very fragile at this point.
5] Transfer 1 tip onto a microscope slide and cut 4-5mm from the growing tip (site of mitosis) and keep it.
6] Gently break up (macerate) the root tip with a mounted needle.
7] Add 1 small drop of orcein ethanoic stain and leave for 2 minutes.
8] Add a coverslip and blot with filter paper.
9] View under a microscope and identify the stages of mitosis.
evaluation points
-Low resolution of microscope (systematic error) – use a more detailed microscope with a greater magnification
-Human error in counting numbers of cells (random error) – take a picture of the image in the lens as this should make counting easier
-Not enough time in the solutions to enable successful maceration or staining (systematic error) – leave for 5 minutes longer in future trials
