How to do trihybrid cross

Trihybrid crosses basically represents the combination of three monohybrid crosses.Mendel performed trihybrid cross by considering three pair of contrasting characters. He crossed pea plnt with tall stem, yellow seed colour and round seed (TTYYRR) with plants having dwarf stems, green colour and wrinkled (ttyyrr).F1 generation was having the genotype of Tt Yy Rr with phenotype of tall stem, yellow and round seeds. In F2 generation,
trihybrid ratio is given below as

 Tall yellow round : 27
 Tall yellow wrinkled: 9
 Tall green round : 9
 Dwarf yellow round : 9
 Tall green wrinkled : 3
 Dwarf yellow wrinkle: 3
 Dwarf green round : 3
 Dwarf green wrinkled : 1

Thus phenotypic ratio was 27:9:9:9:3:3:3:1


Here we take the common and easy example of AA BB and CC


trihybrid cross

  • 3
trihybrid cross is between two individuals that are heterozygous for three different traits. We will build on previous examples and again examine pea shape and pea color and then a new trait: pod shape. The same rules as before apply for shape and color (round is completely dominant to wrinkled, and green is completely dominant to yellow). Pea pod shape follows similar rules, with smooth pods being completely dominant to constricted pods. Therefore, homozygous-dominant and heterozygous individuals will have smooth pods, while homozygous-recessive individuals will have constricted pea pods. Our trihybrid cross example: RrYyCc x RrYyCc is a trihybrid cross. The shape of the pea is controlled by one set of alleles, where round is completely dominant to wrinkled: RR = round Rr = round rr = wrinkled The second set of alleles in this example controls the color of the peas. Green is dominant to yellow: YY = green Yy = green yy = yellow The third set of alleles in this example controls the shape of the pea pod. Smooth is completely dominant to constricted: CC = smooth The gametes for each parent in a trihybrid cross would be RYC, RYc, RyC, Ryc, rYC, rYc, ryC, ryc, with one-eighth of a chance for any of them. Cc = smooth cc = constricted

  • 5
What are you looking for?