Examkin

Question

Difficulty: HardGenetics and Heredity

Match each pattern of genetic inheritance on the left with the biological scenario on the right that correctly demonstrates its mechanism.

  • Incomplete DominanceA cross between red-flowered and white-flowered snapdragons produces heterozygous offspring displaying an intermediate pink phenotype.
  • CodominanceAn individual with IAI^A and IBI^B alleles simultaneously and fully expresses both distinct glycoprotein antigens on red blood cell membranes.
  • Polygenic InheritanceContinuous phenotypic variation in human skin tone and adult height is regulated by the cumulative, additive effects of multiple independent gene loci.
  • Sex-Linked (X-Linked) Recessive InheritanceA mutant allele located on the X chromosome is expressed with much greater frequency in biological males (XYXY) because they possess only a single hemizygous copy.

Answer

The correct pairings are: Incomplete Dominance matches the intermediate pink snapdragon phenotype; Codominance matches the simultaneous expression of both A and B blood group antigens; Polygenic Inheritance matches continuous trait variation across multiple gene loci; and Sex-Linked Recessive Inheritance matches the higher trait incidence in hemizygous biological males.
Each genetic term matches its defining physiological and phenotypic characteristics: Incomplete dominance produces an intermediate heterozygous phenotype (pink flowers); codominance results in distinct simultaneous expression of both alleles (type AB blood); polygenic inheritance yields a continuous distribution of traits through additive effects across multiple distinct genes; and X-linked recessive traits show disproportionate male expression due to hemizygosity.

Step-by-Step Solution

1
Differentiate between blended and co-expressed heterozygous phenotypes.
Incomplete dominance yields an intermediate blended trait (red ×\times white →\rightarrow pink), whereas codominance yields simultaneous, unblended expression of both alleles (AB blood type antigens).
This establishes the distinction between allelic interactions at a single gene locus.
2
Analyze multi-locus quantitative traits versus chromosomal location effects.
Polygenic inheritance governs continuous gradations of physical traits (such as height and skin tone) via multiple interacting genes, while sex-linked recessive inheritance explains male vulnerability due to having only one X chromosome.
This pairs the remaining systemic genetic mechanisms to their definitive biological outcomes.

Key Concept

Patterns of Non-Mendelian and Chromosomal Inheritance
Estimated Time:1m 30s
Rate this question

Topics

Genetics and Heredity

More questions from this topic