Why offspring differ from their parents, and how Mendel's pea plants revealed dominant and recessive traits, the 3:1 ratio and the 9:3:3:1 ratio.
3 lessons, about 1 h 25 min3 simulations11 problems3 practice questionsPython in every lesson
Created by StemPy LabChildren look like their parents but never exactly like them. DNA copying is never perfect, so every kind of reproduction makes small variations. Sexual reproduction mixes the DNA of two parents and makes far more. Variations build up over generations, and some help their owners to survive.
Gregor Mendel crossed garden peas with contrasting traits. Crossing pure tall with pure short gave an F1 that was all tall. Self-pollinating the F1 gave tall and short plants in the ratio 3 : 1. Each trait is set by a pair of gene copies, one from each parent. The dominant copy shows over the recessive one.
In a dihybrid cross Mendel followed two traits at once. Pure round yellow crossed with pure wrinkled green gave an F1 all round yellow. The F2 had four kinds of seeds in the ratio 9 : 3 : 3 : 1, including two new mixes. So the genes for seed shape and seed colour are inherited independently.
Log in to join the discussion.
Loading…