Laboratory work 7: studying cross results of cotton, tomato and four-o’clock from herbarium specimens
A herbarium is a collection of dried plant specimens fixed on paper; it lets you view and compare the structure and traits of a plant. In this work you compare varieties of three plants: tomato fruit shape and colour, cotton fruiting branch and fibre colour, four-o’clock flower colour. For each trait you find which forms appear in the parent varieties and in F1 (or use the textbook data) and write it in the table as dominant, recessive or intermediate: if F1 repeats one parent, that trait is dominant; if it lies between the two, it is an intermediate trait (incomplete dominance). A herbarium shows only the phenotype; the genotype can be found from the cross results and the numbers of offspring. Handle the specimens carefully, follow the teacher’s instructions, do not put specimens in your mouth, and wash your hands at the end.
“Herbarium table”. Using the herbarium or pictures given by the teacher, fill the table: plant — trait — dominant — recessive — intermediate. Defend your result in class.