In tomatoes, the three mutant traits, dwarfness, green flesh, and white flowers,

Question

In tomatoes, the three mutant traits, dwarfness, green flesh, and white flowers, are due to the homozygous recessive state of the genes d, gf, and wf (respectively). A dwarf, green-fleshed, white-flowered plant is crossed as the pollen parent to the homozygous normal plant.

a. Diagram the cross, using the forked-line method, to determine the F2 phenotypic ratio. Include phenotypes with the appropriate expected ratios.

b. If the F1 were testcrossed, what would be the expected phenotypic and expected genotypic ratios? Y

Explanation / Answer

dwarfness, ----------d

green flesh, ------gf

and white flowers, -----wf

homozygous recessive state of the genes    dd   g f gf      wf wf

homozygous normal plant.------------DD          GF GF          WFWF

dd   g f gf      wf wf

GAMTES -----------d gf wf

==============

DD          GF GF          WFWF

GAMTES -----------D GF WF

F1 OFFPRING         Dd         GF gf         WFwf

All offspring are normal

=============

Selfing F1 OFFPRING        

Dd         GF gf         WFwf       x      Dd         GF gf         WFwf

DGFWF

dgfwf

Trihybrid cross

Number of offspring are    64

phenotype ratio----------27:9:9:9:3:3:3:1

Dd         GF gf         WFwf      

D         d             GF            gf               WF           wf      

D GF WF

D GF wf      

D gf   WF

D gf   wf      

d GF wf      

d gf   WF

d gf   wf      

DGFWF

dgfwf

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