Question

Red rose color is produced by either of two genes, R/r and I/i. The dominant alleles of both these genes produce red pigment, and one of these genes is enough to produce a red flower. The recessive alleles are nonfunctional and produce no pigment (remember that no pigment = white.
Required:
What is the overall phenotypic ratio from the cross above?

Answer 1

Answer:

3:1

Explanation:

To find out the phenotypic ratio, we need to do a Punnet Square.

We know that R and I are the dominant alleles that produce red flowers, and r and i are the recessive traits.

 ║R ║ r

I ║RI║Ir

i ║Ri║ir

The genotype ratio would be 3 because the dominant traits are present three times (RI, Ir, and Ri) and 1 for the recessive trait since it only appears once in the Punnet Square (ir). In conclusion, the phenotypic ratio form the roses are 3:1

Answer 2

Complete question:

Red rose color is produced by either of two genes, R/r and I/i. The dominant alleles of both these genes produce red pigment, and one of these genes is enough to produce a red flower. The recessive alleles are nonfunctional and produce no pigment (remember that no pigment = white.

a. Given the allele combinations below, state the phenotype and expected ratio (as a fraction that would result from a cross of two dibybrid roses. (Ex: A B : Green 9/16)

R-I-

rrI-

R-ii

rrii

b. What is the overall phenotypic ratio from the cross above? (Ex black: 3 yellow : 1 green)

c. What type of epistasis is this? (Note there is a word bank below) Dominant epistasis, Dominant suppression, Duplicate gene action, Recessive epistasis, Complementary gene action No Epistasis

Answer:

• 9/16 R-I-, 3/16 R-ii, 3/16 rrI-, 1/16 rrii
• 15:1
• Duplicate gene action

Explanation:

Available data:

• Red rose color produced by two diallelic genes
• Gene 1: Dominant allele R

                      Recessive allele r

• Gene2: Dominant allele I

                     Recessive allele i

• The dominant alleles of both these genes produce the red pigment
• One of these genes is enough to produce a red flower
• The recessive alleles produce no pigment

a. Given the allele combinations below, state the phenotype and expected ratio (as a fraction) that would result from a cross of two dibybrid roses.

R-I-

rrI-

R-ii

rrii

Cross: Two dihybrids

Parentals) Rr Ii    x     Rr Ii

Gametes) RI, Ri, rI, ri

                RI, Ri, rI, ri

Punnett square)    RI           Ri             rI             ri

                     RI    RRII       RRIi        RrII           RrIi

                     Ri    RRIi        RRii        RrIi          Rrii

                     rI     RrII        RrIi           rrII          rrIi

                     ri     RrIi         Rrii          rrIi           rrii

F1) 9/16 individuals are expected to be red R-I-

    3/16 individuals are expected to be red R-ii

    3/16 individuals are expected to be red rrI-

    1/16 individual is expected to be white rrii

b. What is the overall phenotypic ratio from the cross above? (Ex black: 3 yellow : 1 green)

Red individuals 15/16

White individual 1/16

Phenotypic ratio → 15:1

c. What type of epistasis is this? Dominant epistasis, Dominant suppression, Duplicate gene action, Recessive epistasis, Complementary gene action No Epistasis

Duplicate gene action. There are two genes involved in the expression of a phenotype, and the presence of at least one dominant allele is enough to produce the dominant phenotype (in this case, red color). The phenotypic ratio of this interaction is always 15:1. This is an example of dominant duplicate genes.