Traits you can check
Eight inherited characteristics common among people, every one of which you can check on yourself in the next minute. That is what makes this the right place to start.
| Characteristic | One form | The other form |
|---|---|---|
| Ear lobes | Attached to the side of the head | Hanging free |
| Tongue | Can be rolled into a tube | Cannot be rolled |
| Thumb | Straight when held up | Bends back at the joint |
| Hairline | Comes to a point on the forehead | Runs straight across |
| Cheeks | Dimple when you smile | No dimple |
| Hair | Curly | Straight |
| Interlocked fingers | Left thumb ends up on top | Right thumb ends up on top |
| Skin colour | Lighter | Darker |
Figure to be added
The last row is not like the other seven
Seven of these are either / or — you can roll your tongue or you cannot. Skin colour is not; it runs through a continuous range with no line down the middle, because several characteristics act together to produce it. Most of this chapter deals with the simple either/or kind, which is exactly why Mendel got a clear answer.
Activity 20.1
Method
- Observe the relatives on your mother's side and on your father's side for the characteristics and abilities above, and draw up a table.
- Using that information, identify which characteristics and abilities have been transmitted from generation to generation.
- Ask whether a characteristic not seen among the relatives you checked has turned up in you, in a brother or sister, or in some other relative.
A characteristic can skip a generation
You will find that many characteristics come down from both sides. But a characteristic none of your relatives has may still appear in a brother or sister — and if you could go further back, you would very likely find it there. An inherited characteristic can pass through several generations unseen and then reappear.