Cells - Investigating Mitosis Flashcards
How do you ensure that your results are valid?
- Eye Piece Graticule: The graticule is calibrated using a stage micrometer.
- Eye Piece Grid Reticule: Use the grid to randomly sample. Ensure you don’t count the cells more than once.
How do you prepare a root tip slide?
- Stand the beaker on a bench mat before adding approx. 10ml of hydrochloric acid (5 mol dm -3 )
- Place about 2 cm of root tip in the acid and leave for 15 minutes.
- Set up your microscope while you are waiting.
- Rinse the root tip in distilled water in the watch glass.
- Cut off the root tip (1mm) and place on a microscope slide.
- Cover the section with toluidene blue stain and macerate with the mounted needle to separate the cells.
- Continue to macerate until the tissue is well broken and the cells are stained dark blue.
- Add a cover slip and with gentle finger pressure ‘spread’ the material and blot at the same time by using a folded filter paper between finger and slide.
- Look carefully at all slides for cells undergoing mitosis. Chromosomes should stain dark blue. Repeat for several fields of view.
- Record your data in a suitable table.
- Calculate the mitotic index.
What is the mitotic index?
The mitotic index is the ratio between the number of cells in mitosis and the total number of cells. It can be determined by analysing micrographs and counting the relative number of mitotic cells versus non-dividing cells.
mitotic index = cells in mitosis / total number of cells
How could you use the mitotic index to identify cancerous tissue?
Compare the mitotic index of healthy tissue to cancerous tissue. The higher value is cancerous.
How do you identify a cell in interphase?
When a cell was in interphase, we identified it by looking for a dark circle. Sometimes there’d be two lighter circles within it where the dye hadn’t reached. Most of the cells were in interphase, as this is the stage that cells spend the longest time in.
How do you identify a cell in prophase?
When we saw thick strands of DNA loose in the cell, we said this was prophase. If you are viewing early prophase, you might still see the intact nucleolus, which appears like a round, dark blob.
How do you identify a cell in metaphase?
A cell was in metaphase when the chromosomes lined up in the middle of the cell. We also saw thin-stranded structures (spindle fibres) that appeared to radiate outward from the chromosomes to the outer poles of the cell, but these were harder to see.
How do you identify a cell in anaphase?
During early anaphase, we saw the chromosomes clearly separating into two groups. During late anaphase, these groups of chromosomes were on opposite sides of the cell.
How do you identify a cell in telephase?
When the cell was in telophase, we saw the DNA at either pole. It may still be in its condensed state or thinning out. The new nucleoli were sometimes visible, and we sometimes noted a cell membrane (or cell wall) between the two daughter cells.
