Mendelian Genetics
MENDELIAN GENETICS
Gregor Mendel
- 19th century monk
- Discovered the basic principles of heredity via experiments with pea plants
Character
Heritable feature (such as flower color or seed shape)
Trait
Variant of a character (such as purple or white for flower color)
MENDEL'S EXPERIMENTS
1) Cross true-breeding purple-flowered plants to true-breeding white-flowered plants – P Generation
True-breeding
When pea-plants self-pollinate, they only ever produce offspring with the same trait (eg, purple-flowered plants always produce purple-flowered offspring)
2) Allow hybrid F1 generation to self-pollinate – This generation was always all purple-flowered
Hybrid
Offspring of the cross between two true-breeding parents
3) Observe the offspring of the F1 generation (F2 generation) – These exhibited a 3:1 ratio of purple-flowered plants to white-flowered plants
MENDEL'S MODEL OF INHERITANCE
1) Alternative forms of heritable factors (genes) account for variations – called alleles
2) For each character, an organism inherits two alleles (one from each parent)
3) If the two alleles differ, the dominant allele will determine the appearance and the recessive allele has no noticeable effect
4) The two alleles separate into different gametes during gamete formation – Law of Segregation