Question

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A true-breeding maize plant with purple kernels is crossed with a true-breeding maize plant with colorless kernels, known to be homozygous for the presence of an independent Ac element. The F1 progeny are all purple. The F1 plant is mated with a colorless-kernel parent homozygous for the mutable c1-m1 allele. The progeny of the cross show a phenotypic ration of 2 colored: 1 spotted: 1 colorless. The c1-m1 allele is due to the insertion of a Ds element into the C1 gene. What is the genotype of the original purple parent?

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1. C1C1 Ac+Ac+
2. C1C1 Ac+Ac-
3. C1C1 Ac-Ac-
4. c1-m1 c1-m1 Ac+Ac+
5. c1-m1 c1-m1 Ac+Ac-
6. c1-m1 c1-m1 Ac-Ac-
7. c1c1 Ac+Ac+
8. c1c1 Ac+Ac-
9. c1c1 Ac-Ac-

Answer 1

It is very important to know about the transposans elements in maize.transposable elements are DNA sequences that move from one location to another location in the genome.

The progenybin F1 are homozygous because of Ac transposans.The Ac Activator element is responsible for autonomous .hence the F1 progeny is homozygous with purple colour.

In the next generation the c1-m1 is colorless kernable mutant allele which is c1 and mutable allele is m1.and the progeny is 2 colored 1spotted and 1 colour less is because of Ds is the Dissociation element requires an Ac element to transpose.

Finally the original genotype of the purple plant is given below

c1-m1 c1-m1 Ac+Ac-