Mendelian Genetics
Mendelian Genetics
* Pea plants have several advantages for genetics. * Pea plants are available in many varieties with distinct heritable features (characters) with different variants (traits). * Another advantage of peas is that Mendel had strict control over which plants mated with which. * Each pea plant has male
(stamens) and female
(carpal) sexual organs. * In nature, pea plants typically self-fertilize, fertilizing ova with their own sperm. * However, Mendel could also move pollen from one plant to another to cross-pollinate plants. * In a typical breeding experiment, Mendel would cross-pollinate (hybridize) two contrasting, true-breeding pea varieties. * The true-breeding parents are the P generation and their hybrid offspring are the F1 generation. * Mendel would then allow the F1 hybrids to self-pollinate to produce an F2 generation. * It was mainly Mendel’s quantitative analysis of F2 plants that revealed the two fundamental principles of heredity: the law of segregation and the law of independent assortment.
2. By the law of segregation, the two alleles for a characters are packaged into separate gametes * If the blending model were correct, the F1 hybrids from a cross between purple-flowered and white-flowered pea plants would have pale purple flowers. * Instead, the F1 hybrids all have purple flowers, just a purple as the purple-flowered parents. * When Mendel allowed the F1 plants to self-fertilize, the F2 generation included both purple-flowered and white-flowered plants. * The white trait, absent in the F1, reappeared in the F2. * Based on a large sample size, Mendel recorded 705 purple-flowered F2 plants and 224 white-flowered F2 plants from the original cross.
Vocab:
* Character –heritable feature * Trait – each variant for a character * True-breeding – plants that self-pollinate all offspring are the same
* Pea plants have several advantages for genetics. * Pea plants are available in many varieties with distinct heritable features (characters) with different variants (traits). * Another advantage of peas is that Mendel had strict control over which plants mated with which. * Each pea plant has male
(stamens) and female
(carpal) sexual organs. * In nature, pea plants typically self-fertilize, fertilizing ova with their own sperm. * However, Mendel could also move pollen from one plant to another to cross-pollinate plants. * In a typical breeding experiment, Mendel would cross-pollinate (hybridize) two contrasting, true-breeding pea varieties. * The true-breeding parents are the P generation and their hybrid offspring are the F1 generation. * Mendel would then allow the F1 hybrids to self-pollinate to produce an F2 generation. * It was mainly Mendel’s quantitative analysis of F2 plants that revealed the two fundamental principles of heredity: the law of segregation and the law of independent assortment.
2. By the law of segregation, the two alleles for a characters are packaged into separate gametes * If the blending model were correct, the F1 hybrids from a cross between purple-flowered and white-flowered pea plants would have pale purple flowers. * Instead, the F1 hybrids all have purple flowers, just a purple as the purple-flowered parents. * When Mendel allowed the F1 plants to self-fertilize, the F2 generation included both purple-flowered and white-flowered plants. * The white trait, absent in the F1, reappeared in the F2. * Based on a large sample size, Mendel recorded 705 purple-flowered F2 plants and 224 white-flowered F2 plants from the original cross.
Vocab:
* Character –heritable feature * Trait – each variant for a character * True-breeding – plants that self-pollinate all offspring are the same