Invertigating Motosis

Question 1

Observing mitosis stage 1

Answer 1

• cut 1 cm from the tip of a growing root as the tip is where growth occurs
• if your using ethano-orcein to stain the cells the tips will need to be fixed in ethanoic acid

Question 2

Observing mitosis stage 2

Answer 2

Prepare a boiling tube containing 1 M hydrochloric acid and put it in a water bath at 60oC

Question 3

Observing mitosis stage 3

Answer 3

Transfer the root tip into the boiling tube and incubate for about 5 minuets

Question 4

Observing mitosis stage 4

Answer 4

• Use a pipette to rinse the root tip will with cold water

- leave the tip to dry on a paper towel

Question 5

Observing mitosis stage 5

Answer 5

Place the root tip on a microscope slide and cut 2mm from the very tip of it then get rid of the rest

Question 6

Observing mitosis stage 6

Answer 6

Use a mounted needle to break the tip open and spread the cells out thinly

Question 7

Observing mitosis stage 7

Answer 7

• add a few drops of stain and leave for a few minuets
• the stain will make the chromosomes easier to see under a microscope
• if your using feulgen you’ll need an extra rinse

Question 8

Observing mitosis stage 8

Answer 8

• place a cover slip over the cells and push down firmly to squash the tissues
• this makes the tissue thinner and allows light to pass through if
• don’t smear the coverslip sideways as it will damage the chromosomes

Question 9

Observing mitosis stage 9

Answer 9

-now you can look at all the stages of mitosis under an optical microscope

Question 10

What’s the first step of using an optical microscope to observe cells?

Answer 10

clip the slide you prepared onto the stage

until the image is in focus

Question 11

What is a stage micrometer?

Answer 11

• it’s a microscope slide with an accurate scale
• it is used to work out the value of the divisions on the eyepiece graticule at a particular magnification
• swapped with the slide containing tissue sample so you can measure the size of the cells

Question 12

What can get in the way of your observations?

Answer 12

Artefacts like

• dust
• air bubbles
• finger prints
• inaccuracies in squashing and staining the sample

Question 13

What is the mitotic index?

Answer 13

• the proportion of cells undergoing mitosis
• a plant root tip is constantly growing so there’s a high mitotic index
• a high mitotic index could also mean that tissue repair is taking place or there is a cancerous growth

Question 13

What’s the second step of using an optical microscope to observe cells?

Answer 13

select the lowest powered objective lens

Question 14

What’s the third step of using an optical microscope to observe cells?

Answer 14

use the coarse adjustment knob to bring yo the stage just below the lens

Question 15

What’s the fourth step of using an optical microscope to observe cells?

Answer 15

look down the eyepiece, move the stage away from the lens

Question 16

What’s the fifth step of using an optical microscope to observe cells?

Answer 16

adjust tbe focus with the fine adjustment knob until the image is clear

Question 17

What’s the sixth step of using an optical microscope to observe cells?

Answer 17

If you need to see the slide with greater magnification swap to a higher power objective lens and refocus

Question 18

What is an eye piece graticule?

Answer 18

it’s fitted into the eye piece like a transparent ruler with numbers but no units

Question 19

Where are artefacts most common?

Answer 19

• electron microscopes
• specimens need a lot of preparation
• the first scientists to use these microscopes could only distinguish between artefacts and organelles by repeatedly preparing specimens in different ways to see what was there and what wasn’t