Rr r rr rr r rr rr in a classic experiment using pea shape, mendel conducted two separate genetic crosses. in the first cross the parent plants were “true breeding” for pea shape; one had round peas ( r )and the other had wrinkled (r). the first cross produced a filial 1 generation of all round peas. in the second cross, mendel bred plants from the filial 1 generation. this cross produced different results. out of approximately 1000 plants, about 75% were round and 25% were wrinkled. from these experiments, mendel developed four hypotheses. they include all but a) one heritable factor may be dominant and mask the other factor. b) any organism that "shows" a heritable factor must be homozygous. c) an organism has two "heritable factors", now called genes, one from each parent. d) a sperm or egg carries only one heritable factor for each trait in the offspring.