Track quiz
Here are the rules first. Each lab uses these exact words.
| Idea | The rule |
|---|---|
| Resemble both, match neither | Each trait has two gene copies, one from each parent. One copy can hide the other. A child may match one parent in shape. It may match the other in colour. |
| The man who counted | Mendel used true-breeding lines, crossed them by hand, and counted every offspring. Counts turn a guess into a pattern you can test. |
| The hidden one comes back | A gene pair has two copies. A dominant copy shows in the plant. A recessive copy shows only when both copies are recessive. |
| The count is the argument | Two Tt plants are crossed. Each seed gets T or t from each parent. So the four pairs TT, Tt, Tt and tt are equally likely. Three of them give tall plants. One gives a short plant. |
| Two traits at once | Two gene pairs are passed on separately. That gives sixteen equally likely boxes. In big counts, the looks come near nine, three, three and one. |
| Which contribution decides | A parent with a mixed pair can pass either kind. A parent with a matching pair always passes the same kind. In people, the father has the mixed pair, XY. So the father's sperm decides the sex. |
| The laws in plain words | Dominance: one form of a gene can hide another. Segregation: a pair separates, and each parent passes one gene. Independent assortment: two gene pairs sort into gametes independently. |
A true tall pea, TT, meets a true short pea, tt. What are the F1 plants?
Two Tt plants give 200 seedlings. About how many grow short?
Two RrYy plants are crossed. About how many of 480 seeds are wrinkled-green?
In people, what can a mother's egg carry?
What decides the sex of a child?
A Tt plant is crossed with a tt plant. What share of the seeds grow tall?
A gardener counts 12 F2 seedlings and finds 12 tall. Does this disprove 3 : 1?
Round seeds are dominant. A wrinkled-seed plant has two round-seed parents. Is that possible?
Chapter 8 of your Class 10 Science book is Heredity. Read it with the three rules in mind.
The next chapter is Light – Reflection and Refraction.