) Peanuts have two types of growth behavior: runner, which grows low to the grou
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) Peanuts have two types of growth behavior: runner, which grows low to the ground, and bunch, which grows upright and branched. A true-breeding line of runner peanuts is crossed to a true-breeding line of bunch peanuts. All of the F1 progeny grow as runners, so runner appears to be dominant. These F1 runner peanuts are then crossed to true-breeding bunch peanuts (NOT a self-cross) and the progeny show both phenotypes in a ratio of 3 bunch : 1 runner. Clearly one gene cannot explain this. How many genes are involved in the growth behavior phenotype, and what must the genotypes in the cross be? Assume recessive loss-of function mutations are involved.Explanation / Answer
THIS WILL BE HELPFUL FOR YOU ANS PL RATE ME 1ST The genotype of true breeding line of runners is: RRbb The genotype of true breeding line of bunch peanuts is: rrBB The genotype of the F1 will be BbRr. This is crossed with a true breeding line of bunch peanuts [ rrBB]. The gametes from the heterozygote will be BR, Br, bR and br. The gametes from the true breeding line will be Br. Here BBRr gives bunch phenotype due to the presence of two dominating alleles of B. BBrr also gives bunch phenotype BbRr gives runner phenotype due to the presence of heterozygous genotype Bbrr gives bunch phenotype In this way we get a 3:1 phenotypic ratio.
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