SOCR 330 Lecture Notes - Chromosome, Dihybrid Cross, Zygosity
Document Summary
Began breeding experiments with peas (pisum satiuum) in 1854. Published findings in 1865 but significance not realized until 1900. Gene for stem height in pea plants has two different forms or alleles. Tall allele is dominant (only parental phenotype seen in f1) Dwarf allele is recessive (parental phenotype missing in f1 but reappears in f2) F2 generation segregates into two phenotypic classes (tall and dwarf) in 3:1 ratio. Whichever allele is present (tall or dwarf version of the gene) it will always be located at a particular point or locus on the chromosome. Pea plants are diploid: 2 sets of chromosomes. Two copies of a gene are present at any given locus. If both copies are the same allelic version of the gene, the pea plant is homozygous at that locus (e. g. tt or tt) If two different alleles are present, the pea plant is heterozygous at that locus (e. g. tt)
