Question

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GENETICS (Refer to the following information to answer this question):

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 the white flower is governed by the allele r(rr).

The horticulturalist plans to cross a geranium that i true-breeding for red flowers that is true-breeding for white flowers. Which punnett square best describes this cross?

A)
_| R | r |
R| RR | Rr |
r| Rr | rr |

B)
_| r | r |
R| Rr | Rr |
r | rr | rr |

C)
_| r | r |
R| Rr | Rr |
R| Rr | Rr |

Answer 1

Answer:C

The true breed red flower's genottype is RR and for white flower is rr. So horticulturalist plans to cross a geranium that is true breeding for red color and for white color will best describe by the cross between RR and rr.

      r       r

R    Rr     Rr

R    Rr     Rr

Answer 2

Answer:

C

Explanation:

The horticulturist is trying to perform a monohybrid cross involving a single gene coding for flower colour in geranium. The allele for red flower (R) is dominant over the allele for the white flower (r) because in an heterozygous state (Rr), the red allele masks the expression of the white allele.

The horticulturist crosses a truebreeding red-flowered geranium with a white-flowered geranium.

Note that, a true breeding plant is a plant that is genetically identical and have identical alleles for a specific trait (flower color in this case). Hence, the alleles of a truebreeding plant is homozygous i.e. same allele

Therefore a truebreeding red-flowered geranium will possess the genotype RR, while a truebreeding white-flowered geranium will have the genotype rr. In a cross using a punnet square, RR will produce gametes R, R while rr will produce gametes r, r.

All the offsprings as seen in the punnet square will possess the genotype Rr, which is heterozygous and phenotypically red-flowered