5. Consider these two alternative pathways involving genes P and R in a flower p

Question

5. Consider these two alternative pathways involving genes P and R in a flower pigm (a) If you cross two plants (P) to each other with the cross: PPrr x ppRR. What color should their F2 progenies have, respectively? In what proportion? Show your work. (b) Which pathway shows interaction between gene two genes epistatic to each other? Explain. ent pathway P and R? In other words, in which pathway are the Pathway 1 Pathway 2 Precursor 1 Precursor 2 Precursor 1 Red Blue Red Coexpression of blue and red pigment derived from different precursors makes purple. Modification of the same precursor leads to first a red pigment and then a purple pigment

Explanation / Answer

Answer:

PPrr (White) x ppRR (Red)----P1

     Pr                pR------------Gametes

              PpRr (purple)-------F1

PpRr x PpRr

Purple = 9/16

Red = 3/16

White = 4/16

b).

Pathway 2 shows interaction between gene P and R.

Recessive Epistasis [9:3:4 Ratio]:

When recessive alleles at one locus mask the expression of both (dominant and recessive) alleles at another locus, it is known as recessive epistasis. This type of gene interaction is also known as supplementary epistasis.

There are three colours, purple, red and white. The purple colour develops in the presence of two dominant genes (R and P), red colour in the presence of a dominant gene R, and white in homozygous recessive condition (rrpp).

Purple = R_P_

Red = R_pp

White = rrP_ or rrpp

RP Rp rP rp RP RRPP (purple) RRPp (purple) RrPP (purple) RrPp (purple) Rp RRPp (purple) RRpp (red) RrPp (purple) Rrpp (red) rP RrPP (purple) RrPp (purple) rrPP (white) rrPp (white) rp RrPp (purple) Rrpp (red) rrPp (white) rrpp (white)

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