Question

Concerning the four corn genes below

Trait Gene Alleles Aleurone color Aleurone calor R Phenotypes Color inhibitor, colorless aleurone (dominant to Colored aleurone (dominant to Nullallele, colorless aleurone Red aleurone Null allele, colorless aleurone Modifins red alourone (R allele) to purple Null allele, does not modify R allele (red alourone) Yellow endosperm White endosperm Aleurone color Endosperm colory

a) For the following corn genotypes, indicate the expected kernel colors.

1) Cc Rr pp yy

2) CC rr PP yy

3) Cc Rr Pp YY

4) CIc Rr Pp yy

5) CIC Rr pp Yy

b) From the following corn crosses, list all of the expected genotypes, corresponding phenotypes, and the ratios (phenotypic and genotypic) that you would expect among the progeny. List only the genes that are segregating, not the genes that are homozygous for the two parents.

1) CC Rr Pp YY x CC Rr Pp YY

2) CIC RR PP Yy x CIC RR PP Yy

Answer 1

a)
1) Cc Rr pp yy

This corn will have Red Kernels. since the plant has the genotype Rr, it will produce Red Kernels, and the absence of the Color inhibitor allele, (Cl) means that the Kernels develop color. The absence of the Aleurone modifier (pp) means Kernels are not Purple.

2) CC rr PP yy

The Kernel will be white. This is because the Alleurone layer is colorless, as the Alleurone color gene is homozygous recessive (rr). The endosperm is white colored, which will lead to a white kernel.

3) Cc Rr Pp YY

This Kernel will be Purple. The colored aleurone gene(Cc), allows color development, Aleurone Color gene(Rr) allows red color to develop, and the color modifier gene (Pp), modifies the color to Purple.

4) CIc Rr Pp yy

This Kernel will be White. The presence of the Aleurone color inhibitor allele (Cl), prevents the Aleurone color gene(Rr) from developing color. Therefore, the Endosperm color will be visible. Here the endosperm color is white since two recessive alleles are present (yy)

5) CIC Rr pp Yy

This Kernel will be Yellow. The presence of the Aleurone color inhibitor allele (Cl), prevents the Aleurone color gene(Rr) from developing color. Therefore, the Endosperm color will be visible. Here the endosperm color is Yellow as a yellow allele is present (Yy).

b)

1) CC Rr Pp YY x CC Rr Pp YY

The progeny produced from this cross is (Note that all progeny will have the CC YY genotype for the Colored Aleurone gene and the Endosperm color gene):

		Gametes of CC Rr Pp YY parent
		RP	Rp	rP	rp
Gametes of CC Rr Pp YY Parent	RP	RR PP	RR Pp	Rr PP	Rr Pp
Rp	RR Pp	RR pp	Rr Pp	Rr pp
rP	Rr PP	Rr Pp	rr PP	rr Pp
rp	Rr Pp	Rr pp	rr Pp	rr pp

The progeny types and the progeny phenotypes produced are (all progeny are CC YY):

• RR PP --> Purple Aleurone
• RR Pp --> Purple Aleurone
• RR pp --> Red Aleurone
• Rr PP --> Purple Aleurone
• Rr Pp --> Purple Aleurone
• Rr pp --> Red Aleurone
• rr PP --> Colorless Aleurone, Yellow Kernels
• rr Pp --> Colorless Aleurone, Yellow Kernels
• rr pp --> Colorless Aleurone, Yellow Kernels

The genotypic ratios are:
RR PP : RR Pp : RR pp : Rr PP : Rr Pp : Rr pp : rr PP : rr Pp : rr pp :: 1:2:1:2:4:2:1:2:1
The phenotypic ratios are:
Purple Kernel : Red Kernel : Yellow Kernel :: 9:3:4

2) CIC RR PP Yy x CIC RR PP Yy

The progeny produced from this cross is (Note that all progeny will have the RR PP genotype for the Aleurone Color gene and the Aleurone Color modifier gene):

The progeny types and the progeny phenotypes produced are (all progeny are RR PP):

• CLCL YY --> Colorless Aleurone, Yellow Kernels
• CLCL Yy --> Colorless Aleurone, Yellow Kernels
• CLCL yy --> Colorless Aleurone, White Kernels
• CLC YY --> Colorless Aleurone, Yellow Kernels
• CLC Yy --> Colorless Aleurone, Yellow Kernels
• CLC yy --> Colorless Aleurone, White Kernels
• CC YY --> Purple Kernels
• CC Yy --> Purple Kernels
• CC yy --> Purple Kernels

The genotypic ratios are:
CLCL YY : CLCL Yy : CLCL yy : CLC YY : CLC Yy : CLC yy : CC YY : CC Yy : CC yy :: 1:2:1:2:4:2:1:2:1

The phenotypic Ratios are:

Yellow Kernels : White Kernels : Purple Kernels :: 9:3:4