In maize, kernels are usually purple in color, but a recessive allele p prevents

Question

In maize, kernels are usually purple in color, but a recessive allele p prevents the final step in pigment synthesis, leaving the kernel of pp plants red. Dominant alleles of unlinked genes A, C, and R are all required for synthesis of the red pigment. Determine the phenotype of the F1 in a cross of pure breeding red plants with aaccrrPP plants ?which have yellow kernels). What will be the frequency of red, purple, and yellow kernels produced when the F1 is crossed to an aaccrrpp tester? What will the frequencies of the three kernels classes after the F1 is selfed?

Explanation / Answer

yellow kernels ----------aaccrrPP

red kernels ----------- AACCRRpp

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a) cross between pure red breeding plant and yellow kernels plant

aaccrrPP x AACCRRpp

Gametes

ACRp

acrP

AaCcRrPp

F1------------AaCcRrPp - purple colored kernels

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b) when F1 is crossed to aaccrrpp tester

AaCcRrPp x aaccrrpp

Gametes

acrP

ACRP

acrP

ACrP

acrP ACrP

AcrP

acrP AcrP

ACRp

acrP ACRp

AcRp

acrP AcRp

AcrP

acrP AcrP

acrp

aaccrrpp red

Offsprings are

AaCcRrPp - purple

aaccrrpp - red

frequency of yellow, red, purple kernels ----------- 0 : 1 : 1

c) F1 selfed

AaCcRrPp x   AaCcRrPp

Aa             Cc                Rr                Pp

A      a      C     c          R      r           P    p

½                  ½                  ½               ½

AACCRRpp – phenotype ----yellow----------1/4

AaCcRrPp – phenotype ---- purple-------------1/4

AaCcRrPp - phenotype ---- purple----------1/4

aaccrrpp - phenotype ----red----------1/4

Frequency of three kernels 25% yellow : 50% purple : 25% red

Gametes

ACRp

acrP

AaCcRrPp

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