alleryStart learning →A single characteristic gives a phenotypic ratio whose parts total 16. What does that usually indicate?
AA gene carried on the X chromosome only
BA single gene with four alleles in the pool
CAn interaction between two separate genes
DA recessive lethal allele removing one class
Answer & Solution
Correct answer: C. An interaction between two separate genes
1. A dihybrid cross between double heterozygotes gives sixteen equally likely boxes.
2. Two non-interacting genes give 9 to 3 to 3 to 1, whose parts total 16.
3. Interacting gene pairs merge some of those classes but keep the same sixteen boxes underneath.
4. So ratios such as 9 to 3 to 4, 12 to 3 to 1 and 15 to 1 all total 16.
5. A single characteristic showing a ratio that totals 16 is therefore typical of a two-gene interaction.
6. This holds only when the interacting genes are unlinked and still assorting independently.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 12 "Mendel's Experiments and Heredity", section 12.3 Laws of Inheritance_
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