Explain what a phenotypic ratio of 9:7 means.

Question

Explain what a phenotypic ratio of 9:7 ﻿means.

Accepted Answer

∻Answer∻ ⚹ A phenotypic ratio of 9:7 in genetics suggests the interaction of two genes that control a trait, where both genes must have at least one dominant allele to express the dominant phenotype. ⚹ ∻Solution∻ ‖ a ⋮ The 9:7 phenotypic ratio arises from a dihybrid cross involving two genes with epistatic interactions. ‖ ‖ b ⋮ In this scenario, both genes contribute to the expression of a single trait, and the dominant alleles of both genes are required to produce the dominant phenotype. ‖ ‖ c ⋮ The genotypic ratio that leads to this phenotypic ratio can be represented as follows: when $ A- $ is epistatic to $ B- $, the presence of at least one dominant allele $ A $ is necessary to produce the dominant phenotype. If the genotype is $ aa $, the phenotype will be recessive, regardless of the $ B $ gene's alleles. ‖ ‖ d ⋮ The cross $ AaBb \times AaBb $ can produce offspring with the following genotypes and phenotypes: ‖ ‖ ⋮ - 9/16 exhibit the dominant phenotype (at least one $ A $ and one $ B $ allele: $ A-B- $) ‖ ⋮ - 7/16 exhibit the recessive phenotype (either $ aaB- $, $ A-bb $, or $ aabb $) ‖ ∻Key Concept∻ ⚹ Epistasis ⚹ ∻Explanation∻ ⚹ Epistasis occurs when the effect of one gene is dependent on the presence of one or more 'modifier genes'. In a 9:7 phenotypic ratio, the interaction between two genes results in epistasis, where one gene masks or modifies the expression of the other gene. ⚹◊What genetic phenomenon is typically associated with a phenotypic ratio of 9:7?⍭ Generate me a similar question◊‖

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