What phenotypic ratio arises from a dihybrid cross involving one dominant and one recessive allele at one locus and codominant alleles at another?
Understand the Problem
The question is asking about the phenotypic ratio that results from a specific type of genetic cross, specifically a dihybrid cross. It involves the inheritance of one dominant and one recessive allele for one gene and codominant alleles for another gene. To solve this, we need to understand the principles of Mendelian genetics and how these ratios are derived from such a genetic cross.
Answer
Codominance modifies the typical 9:3:3:1 ratio.
The phenotypic ratio arising from a dihybrid cross involving one dominant and one recessive allele at one locus and codominant alleles at another locus depends on how the alleles behave at the codominant locus. Codominance typically results in a modified 9:3:3:1 ratio, but specific ratios can vary.
Answer for screen readers
The phenotypic ratio arising from a dihybrid cross involving one dominant and one recessive allele at one locus and codominant alleles at another locus depends on how the alleles behave at the codominant locus. Codominance typically results in a modified 9:3:3:1 ratio, but specific ratios can vary.
More Information
In a typical dihybrid cross with independent assortment and complete dominance, a 9:3:3:1 phenotypic ratio is expected. Codominance at one locus can alter this ratio depending on the expression pattern of codominant alleles.
Tips
A common mistake is assuming the codominant locus behaves like a completely dominant one, which might lead to predicting the standard 9:3:3:1 ratio without modification.
Sources
- Dihybrid Crosses and Independent Assortment - Biology LibreTexts - bio.libretexts.org
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