Methods

1. From the Tools page, click on normal metaphase plate No. 2 and save it on your C drive (or A drive if you have a diskette). The size of each picture is <50kb. Notice that in this metapahse as far as possible one member of each pair of homolgues has a number beside the centromere. The exercise consists in identifying the other member of the pair and marking it similarly.

2. Click on the photo editor. When you see the screen of the editor, select File>Open, and then choose your metaphase plate.

3. Focus your attention on the banding pattern of chromosome 1, the largest metacentric chromosome, and then identify the other member of pair 1on the metaphase. Using the tools on the left of the editor screen (the button marked 'ABC'), write a '1' near the centromere of the other element of pair 1 on the smaller active window. (NB To paint your numbers in red, select first the paintbrush tool and then the text tool, and then select the small red square on the horizontal line over the active window.)

4. Repeat step 3 for each of the 23 pairs of chromosomes, until you have identified them all. Save the annotated picture using a meaningful name. What is the karyotype of this cell?

b) In this exercise, you could start from the unmarked normal metaphase 4, and using the photoeditor's tools, cut out each chromosome, past it on a word document, and then match the pairs to present the standard image of the karyotype, as seen in the 'Standard karyotype'. You may find this procedure very time-consuming. These are the steps in this procedure;

1. Looking at the metaphase from the editor's screen, identify the chromosome you are going to cut out. Work in numerical order, i.e. 1, 2, 3 etc.

2. From the 'Distortions' menu of the editor, open 'Rotate' and rotate the metaphase until your chromosome stands upright (short arm up).

3. Using the 'Lasoo' tool, draw a narrow boundary around the chromosome, and then from the 'Edit' menu copy it to the clipboard.

4. Minimise the editor screen and open a Word document. You could call this 'Karyotype-1'. Paste the chromosome that you have on the clipboard and format the image. To do this, click on the image and then from the 'Format' menu select 'Picture'. Select the Layout 'In line with the text', and click on the 'Advanced' button, selecting 'wrapping style' as 'square' and 'wrap text' as 'both sides', then ok. This will allow you to move the picture wherever you please on the document.

5. Minimise the word document and enlarge the photo editor, going through the same cycle for the other homologue, match the two homologues up and number them, then repeat the cycle.

6. If you are drawing the chromosomes from 'metaphase 2', call the word document 'normal_karyotype_2'. Showing the banded chromosomes side by side should make obvious any differences in banding pattern.

7. Repeat the process until you have the 23 pairs of chromosomes on the karyotype file. Save.

c) Matching pre-cut chromosomes.- For an example of a simpler drag-and-drop test click as follows; groups A & B, C, D & E, F &G & Sex. This exercise corresponds to metaphase 1 in the 'normal' group. (NB Once on group A & B, click on the => to move to the next group etc.)

d) Result of an 'in situ hybridisation' experiment.

In this exercise, you are asked to identify some chromosome bands where signal from a labelled probe has hybridised.

Download metaphase 3 from the 'Tools' page. Notice that some bands are marked with a red 'dot'. This metaphase is the result of an 'in situ' hybridisation experiment using a probe labelled with a red fluorochrome. You are asked to identify the karyotype location(s) where hybridisation has occurred; naming the chromosome(s) and band(s).

Tools Page