Chickpeas are the third largest legume crop in the world and one of the eight founder crops of agriculture. Chickpea flower color is a useful morphological marker of different strains of chickpea. Of the world collections of chickpeas, 80% produce pink flowers, 19% produce white flowers and 1% produce blue flowers. Two pure-breeding strains of chickpea, Strain A (white flowers) and Strain B (blue flowers) were crossed and the F1 were all pink. The F2 generation (from an F1 X F1) produced: 141 Pink flowers plants 40 Blue flower plants 66 White flower plants A. Explain these results if a single gene is responsible for determining flower color in chickpeas. Give your answer by assigning genotypes, phenotypes and ratios. B. Explain these results if two genes are responsible for determining flower color in chickpeas. Give your answer by assigning genotypes, phenotypes and ratios. C. How would you test which hypothesis (one gene or two genes) is the most likely hypothesis

Answer and Explanation:

a. The enes are responsible for expressing the characteristics of an individual. However, genes responsible for the same trait have different alleles, which make these traits different from each other, as is the case with chickpea flowers. Alleles can be h0m0zygous dominant (AA), recessive h0m0zygous (aa) or heterozygous (Aa), in short, dominant alleles are expressed in capital letters and are always expressed by the organism, so the alleles with greater proportions within an intersection, since they can be expressed in h0m0zygous and heterozygosis. Recessive alleles, however, can only be expressed in h0m0zygous and therefore have a smaller proportion.

B. Chickpeas have a type of dominance called incomplete dominance. This type of dominance occurs when the dominant alleles (AA) do not suppress the expression of the recessive genotype (aa), but joins the one showing an intermediate phenotype to the phenotype of the two alleles. This recessive phenotype can be seen in the heterozygous allele (Aa). Thus, we can see that the dominant flowers have AA alleles and have a white phenotype, while recessive flowers have aa alleles and have a blue phenotype, as explained in the question above. The crossing between these two plants generates an offspring where all the flowers present the pink phenotype, which is the intermediate phenotype between blue and white, in addition, this crossing generated an offspring that presents the Aa phenotype. You can also see this variety of colors at the crossing of the F2 generation, where most plants have the intermediate phenotype (Aa), followed by the dominant phenotype (AA) and followed by the recessive phenotype (aa). All crossings can be seen in attachments.

c. To test the hypothesis of one or more genes responsible for these characteristics, we would have to do biochemical and molecular tests. For that, it would be necessary to make a DNA extraction from the plant, PCR reactions and the isolation of one or more genes related to the color of the flowers.

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