Question

3B. A novice plant breeder is trying to creat a "superdwarf" variety of petunia to use in planters. She starts by crossing two different, pure breeding dwarf varieties together. To her surprise, all the offspring of this cross are tall! When these Fl plants were interbred, the following results were seen in the offspring: 93-tall 68 - dwarf (0 - superdwarf) She comes to you, a genetics expert for an explanation of what is happening a) Explain the inheritance of height in this plant. How many genes are involved? (2 marks) b) Show the genotypes of the parents and the F1 generations. (3 marks) c) Show the genotypes of the gametes produced by the F1 generation. (2 marks) d) For the F2 generation, show what genotypes give rise to tall and what genotypes give rise to dwarf plants. (OK to use dashes where appropriate.) (2 marks) c) What is this phenomenon called? (1 mark)

Answer 1

Answer is given below:

Taco genes , A and B are involved. when , both A and B genes are present, they will give ruse to tall plants. If any one dominant gene is absent, it will give rise to dwarf plants. Dwarf AAbb aaB B Dwarf parental gametes (AB Аарь Tall AaBb X Aabb ab Ab AB AB Aa Bb AABB |AB AABB AABB Tall Tall Tall Tall AaBb АВВЬ A Abb Dwarf Aabb Dwarf Tall Tall aa BB AABB Aabb Tall aaBb Dwarf Dwarf Tall Aabb aaBb aabb AaBb Dwarf Dwarf Tall observed ratio = Tall Dwarf = 93:68 ~ 987 No superdwarf is formed. So, genotype (aabb). is supposed to give rise dwarf. & Expected ratio in F2 = 9.7 (Tall: Dwarf)

Tule genes are involved. Agene Precursor ay Intermediate Одоо i Tour - Dwart Precursor (swart) Intermediate - (Dwarf) No B precursor (Dwarf NO A (e) This is one type of complementary gene enteraction where two pairs of non allelic dominant genes. interact to produce only one phenotypic trait (Tall). But if any of them is present alone does not produce that trait. This is also called Duplicate recessive Epistasis. (6) Conotypes of parent I = AA bb (Pure breeding dwart) parent 2 - aa BB (Pure breeding dwarf) A = Aa Bb All Tall) e i Senotypes of gametes produced by the fi generation are que mentioned above (at previous page). d a generation A_B_ A_bb AaB - dabb = Tall = Dwarf - Dwarf = Dwarf o