Gregor mendel discovered that tall was dominant and short was recessive in pea plants. when he crossed two plants that were both heterozygous tall (tt) he found a 3: 1 ratio of tall to short (75% tall, 25% short) in the offspring leading him to conclude that in a monohybrid cross, the offspring would show a 3: 1 ratio of dominant to recessive phenotypes. a student in a biology lab wants to know if plant flower color is also determined by simple mendelian genetics. first she crosses a true breeding white flowering plant with a true breeding red flowering plant and observes that the offspring all produce red flowers. she then crosses two of these red flowering plants and records the phenotypes of the offspring