Mendel's Laws
Mendel's pea plants showed how traits are inherited.
About this topic
Gregor Mendel, experimenting with pea plants in the 1860s, found that traits are inherited as discrete factors (genes). The law of segregation says each organism carries two alleles for a trait, which separate during gamete formation, so each gamete carries one. The law of independent assortment says alleles of different genes are inherited independently (if on different chromosomes).
Mendel also described dominance. His work was ignored until rediscovered in 1900.
Mendel crossed tall and short pea plants and found that all the first generation were tall, but one quarter of the second generation were short, giving a 3 to 1 ratio. This showed that the short trait had not vanished but was hidden. His law of independent assortment, shown by crossing seed shape with colour, gives a 9:3:3:1 ratio for two traits in a dihybrid cross.
His work was ignored until 1900, long before genes or DNA were known. Today's genetic counselling uses the same logic to predict risks of inherited diseases. Students should know that independent assortment holds only for genes on different chromosomes; genes close together on the same chromosome are linked. Mendel was lucky that the traits he picked behave simply.
Key ideas
- Law of segregation
- Law of independent assortment
- Dominant masks recessive
Quick check
Use cases: where Mendel's Laws helps
- Homework: review the key idea behind Mendel's Laws before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Mendel's Laws without notes.
- Visual learning: play with the interactive lab to see how Mendel's Laws changes when you adjust its inputs.
- Teaching a friend: explain Mendel's Laws in your own words, then compare your version with the key ideas.
Biology underpins medicine, farming, conservation and biotechnology.
Frequently asked questions
What is Mendel's Laws?
Mendel's pea plants showed how traits are inherited.
What will I learn in Mendel's Laws?
Law of segregation. Law of independent assortment. Dominant masks recessive.
Is Mendel's Laws part of Biology?
Yes. It is one of 150 Biology topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Mendel's Laws lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Mendel's Laws?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.