Mendelian Genetics Essay Example

Mendelian Genetics Essay Example Mendelian Genetics Essay Mendelian Genetics Essay 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 o 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 segrega tion 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 ecorded 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 variety * Monohybrid cross – a cross that tracks the inheritance of a single character * P generation – (parental) true-breeding * F1- (first fili al) offspring of P generation * F2 – (second filial) offspring from F1 cross * Allele- alternate version of a gene * Dominate allele – expressed in the heterozygote Recessive allele – not expressed in the heterozygote * Homozygote – pair of identical alleles for a character * Homozygous dominant- BB * Homozygous recessive bb * Heterozygote – two different alleles for a character (Bb) * Genotype – genetic makeup * Phenotype – appearance of an organism Law of Segregation the two alleles for each character segregate during gamete production Law of Independent Assortment – Each set of alleles segregates independently Test cross – designed to reveal the genotype of an organism