Mitosis Practical Flashcards
(22 cards)
Why does acid kill the cells?
denatures proteins
why do we want to kill the cells?
stop mitosis
why is rapid growing root tips good?
growth involves mitosis so we can observe mitosis
why squash root tip between two slides and spread out cells?
to get a single layer of cells to see chromosomes or nuclei when light can pass through
what happens to chromosomes during mitosis?
condense and become visible
why is percentage of cells better than number of cells undergoing mitosis?
allows for comparison between tissues regardless of different numbers of cells in those tissues
what is the mitotic index calculation?
number of dividing cells/ total number of cells
what is the independent variable?
fields of view
what is the dependent variable?
mitotic index
what are the control variables?
-volume and conc of HCl
-length of root left in acid
-amount of stain used
-amount of pressure when you macerate
what should a student do when counting cells to make sure mitotic index is accurate?
examine large number of fields of view to ensure representative sample
why press down firmly on the cover slip?
to make sample thinner so more light can pass through, as tissue will be more squashed so cells are spread apart
why only use the first 2mm from the tip of the root?
where most growth takes place so most mitosis
why is stain used?
to distinguish chromosomes
if you use a different root tip, why is there difference in results?
genetic differences
why is glass slip not pushed sideways?
chromosomes can break
why are root tips good for this practical?
they grow rapidly and growth involves mitosis
why is the hydrochloric acid heated?
makes cells more permeable so stain can enter cells
why does macerating with a mounted needle need to be done well?
ensures cells are broken so stain can enter
why lower the glass slide at a particular angle?
prevents air bubbles entering
why is excess water not added to glass slide?
could lead to artefacts which would block view of root tip cells
what is the mounted needle used for?
breaking open cells and lowering cover slip down to prevent air bubbles
