Question

In watermelon red fruit colour(R)is dominant over cream fruit colour(r).AWater melon plant homozygous for red fruit is crossed with a plant homozygous for cream fruits.The F1 are intercrossed to produce F2.(a)give the genotype and phenotype of the parents the f1 and the f2 (B)give the genotype and phenotype of the offspring of a back cross between the f1 and the red fruit colour homozygous parent (c) give the genotype and phenotype of a back cross between the f1andthe cream fruit colour homozygous parent How to answer this question

Answer 1

We have, R as the dominant allele, and r as the recessive allele. 

Now homozygous red (RR) crossed with homozygous cream (rr) will give our F1 generation- 

RR × rr → Rr (Heterozygous) 

If we self cross Rr, then we will get the F2 generation, -

Rr × Rr → RR, Rr, Rr, rr 

Now, (a)  Genotype and phenotype of F1 generation- 

               Genotype - 1
               Phenotype -1
 (Because of a single result)

   Genotype and phenotype of F2 generation- 
              Genotype - 1:2:1
               Phenotype - 3:1
(b) For backcross, we have F1 gen (Rr) and red homozygous (RR) , so we will get, 

    Rr × RR → RR, Rr 
  
Genotype here will be, 1:1 
Phenotype, again will be 1 (because R is dominant)

(c) For backcross between, F1 gen (Rr) and homozygous cream (rr), we get, 

   Rr × rr → Rr, rr

 Genotype again is 1:1 
and phenotype also, 1. 

Hope this helps.