117. In trihybrid, when all gene show complete linkage then what is ratio of test cross :-
- 1:1:1:1:1:1:1:1
- 1:1
- 1:1:1:1
- 9:3:3:1
Dear Student,
To answer this question we will use following example:
A trihybrid test cross of a heterozygous genotype (Yy Rr Tt) with its homozygous recessive (yyrrtt) parent. This cross, where all the genes shows complete linkage gives the phenotypic ratio-of 1:1:1:1:1:1:1:1 as follows:
| Heterozygous genotype | Homozygous recessive parent | |
| Genotype | YyRrTt | yyrrtt |
| Gametes | (YRT)(YRt)(YrT)(Yrt)(yrT)(yRt)(yrT)(yrt) | (yrt) |
Ratio = (1:1:1:1:1:1:1:1 )
1/8 Yy Rr Tt (Yellow, Round, Tall): 1/8 Yy Rr tt (Yellow, Round, Dwarf): 1/8 Yy rr Tt (Yellow, wrinkled, Tall): 1/8 Yyrrtt (Yellow, Wrinkled, Dwarf):1/8 yyRrTt (Green, Round, Tall): 1/8 yy Rr tt (Green, Round, Dwarf): 1/8 yy rr Tt (Green, wrinkled, Tall): 1/8 yy rr tt (Green, wrinkled, Dwarf).
Option 1 is correct. In trihybrid, when all gene show complete linkage then phenotypic ratio of test cross is 1:1:1:1:1:1:1:1.
Regards,