Q1.
How many combinations can you make with just these three pairs of characters?
Answer
Eight. One bead is picked from each of the three pairs, and each pair offers two choices.
combinations = 2 × 2 × 2 = 23 = 8
| No. | Pair 1 (green) — hair colour | Pair 2 (blue) — hair type | Pair 3 (red) — eye colour |
|---|---|---|---|
| 1 | light green — blonde | light blue — straight | light red — brown |
| 2 | light green — blonde | light blue — straight | dark red — black |
| 3 | light green — blonde | dark blue — curly | light red — brown |
| 4 | light green — blonde | dark blue — curly | dark red — black |
| 5 | dark green — black | light blue — straight | light red — brown |
| 6 | dark green — black | light blue — straight | dark red — black |
| 7 | dark green — black | dark blue — curly | light red — brown |
| 8 | dark green — black | dark blue — curly | dark red — black |
Combination 1 in the list is the one drawn in Fig. 11.9 — blonde and straight hair with brown eyes.
Why the beads model meiosis correctly: the three pairs sit on three different chromosomes, and when the chromosome pairs line up in meiosis, the way one pair happens to be oriented has no effect on how the next pair is oriented. Picking a bead at random from each pair, independently, is exactly that. This independent separation of pairs is what the chapter means when it says "the chromosomes of each pair separate so that each gamete receives only one chromosome from each pair".