Tortoise Sequencing

• identify species
• sequencing
• tortoise trees
• which is which?

You have seven baby tortoises and you know 4 are from Madagascar.. Since the four from Madagascar are more closely related to one another than they are to the other tortoises, you can find them by looking at their genes and measuring the differences in their DNA (or RNA in this case).

In order to see which tortoises are most closely related, you sequenced 1355 base pairs (bp), including the 12S and 16S rRNA and cytochrome b genes from each tortoise. Below are samples of the gels you obtained.

As a geneticist, your next step is to compare the gels and count the differences in the bases. Click here to see how you would compare the gels. Since we have so many base pairs, we wouldn't do this by hand; a computer would do it for us.

Click below to have the computer count the differences for you. Look for the results in the chart below. RUN THE ANALYSIS

How do you read this chart? How do you read this chart?

Have you ever looked at the back of a road atlas and seen those really big charts that show the distance between major cities? Well this is just like that. What this chart is doing is organizing the difference between those 7 data sets in a way in which you can easily compare all 7. If you want to know the difference between Species B and Species E, go down the first column to E and then across the E row to species B and then down the B column to species E where you would find 7%. That number means that 7% of the base pairs were different between species B and species E.

The dashed lines that go diagonally down the chart are in the boxes that would compare a species to itself. Just like there is no distance between Atlanta and Atlanta on a mileage chart, comparing species A to species A is not useful, so a dash is placed there. There are no numbers above the dashed lines because these numbers would just be duplicates of the ones below the lines. Comparing B and E is the same thing as comparing E and B so the chart only gives you the numbers once.