A horticulturalist wants to produce geraniums with specific characteristics. She knows that the trait of red flowers is governed by the allele R(RR and Rr) and the trait of white flowers is governed by the allele r(rr).

Question

The horticulturalist plans to cross a geranium that is heterozygous for red flowers with a geranium that is true-breeding for white flowers.

Which Punnett square best describes this cross?

Responses

r r
R Rr Rr
r rr rr


r r R uppdercase R lowercase r uppercase R lowercase r r lowercase r r lowercase r r

R r
R RR Rr
r Rr rr


R r R uppercase R R uppercase R lowercase r r uppercase R lowercase r lowercase r r



R r
R RR Rr
R RR Rr

Answer 1

To solve this problem, we need to set up a Punnett square for the cross between a heterozygous geranium for red flowers (genotype Rr) and a true-breeding geranium for white flowers (genotype rr).

Here's the breakdown of the alleles involved:

• The heterozygous geranium has the genotype Rr, which can produce gametes R and r.
• The true-breeding white flower geranium has the genotype rr, which can only produce the gamete r.

Now we set up the Punnett square:

          r       r
       ----------------
    R |    Rr     |   Rr   |
       ----------------
    r |    rr      |   rr   |
       ----------------

From the Punnett square:

• The possible genotypes of the offspring are:
  • 50% Rr (red flowers)
  • 50% rr (white flowers)

Now, we can identify the correct option among the choices provided:

1. Incorrect:

     r  r
    R Rr Rr
    r rr rr
   

   This layout does not match the correct setup.

2. Incorrect:

   r r R uppdercase R lowercase r uppercase R lowercase r r lowercase r r lowercase r r
   

   This does not represent a standard Punnett square.

3. Correct:

   R r
   R RR Rr
   r Rr rr
   

   This option shows the correct arrangement of the alleles, but the genotypes need to be Rr and rr, not RR and Rr.

4. Incorrect:

   R r
   R RR Rr
   R RR Rr
   

   This layout is also incorrect as it shows RR as a possibility.

Out of the provided options, none correctly represent the cross with proper labels and setup. However, the closest correct structure was option 3, but you need to correct the genotypes in your response.

For clarity, the correct result of the cross can be summarized as:

• Genotype: 50% Rr (red), 50% rr (white).