Dihybrid Crosses The Law of Independent Assortment Independent
Dihybrid Crosses The Law of Independent Assortment
Independent Assortment • The inheritance pattern of one trait will not affect the inheritance pattern of another • Independent assortment occurs during meiosis • For a single human gamete, the possible ways chromosomes may assort is astounding: 223 = 8, 388, 608 possible combinations
Dihybrid Cross In snapdragons, tallness (T) is dominant to dwarfness(t), while red color is due to gene (R) and white to its corresponding allele (r). The heterozygous condition results in pink (Rr) flower color. A dwarf pink snapdragon is crossed with a plant homozygous for tallness and red flowers. Give the possible genotypes and corresponding phenotypes for all of the possible F 1 generation.
Step #1: Determine Genotypes of Parents “A dwarf pink snapdragon is crossed with a plant homozygous for tallness and red flowers. “ Dwarf pink = tt. Rr Homozygous tall, red = TTRR
Step #2: Determine Genotypes of Gametes “A dwarf pink snapdragon is crossed with a plant homozygous for tallness and red flowers. “ Dwarf pink = tt. Rr t. R tr Homozygous tall, red = TTRR TR TR
Step #3: Punnett Square The Punnett square determines the genotypes of the offspring Gametes from dwarf pink parent Gametes from TALL red parent TR TR TR t. R Tt. RR Tt. RR tr Tt. Rr Tt. Rr TR
Step #4: Identify Phenotype Ratios in Offspring Tt. RR Tall, red = 8/16 Tall, pink = 8/16 Tt. Rr Tt. RR Tt. Rr Tall, white = 0/16 Short, red = 0/16 Short, pink = 0/16 Short, white = 0/16
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