Question

Question 14 6 pts Glossy leaf (g) and red aleurone (r) are two recessive alleles in maize. A hybrid of unknown origin is testcrossed and among 1,000 progeny 275 were wildtype (GR), 270 were red and glossy (gr), 225 were red (Gr) and 230 were glossy (g R). Assuming that the parents of the dihybrid were pure-breeding, which of the following could have been the phenotype of one of the dihybrid's parents? O glossy O red O red and glossy O any of these O none of these

Answer 1

Let the parents of the dihybrid cross with homozygous dominant wildtype(GGRR) be crossed with homozygous recessive red and glossy(ggrr).

Parental generation: GGYY $\times$ ggrr

Gametes: GY $\times$ gr

F1 generation: GgRr (wildtype)

This hybrid F1 is crossed with homozygous recessive red and glossy(ggrr) gives the following results:

GgRr  $\times$ ggrr

Gametes: GR Gr gR gr gr  

the cross yeilds one wildtype(GgRr) (25%), one red(Ggrr) (25%), one glossy(ggRR) (25%) and one red & glossy(ggrr) (25%). So the required phenotype of one of the dihybrid parent is red and glossy.