A variety of pea plant called Blue Persian produces a tall plant with blue seeds. A second variety of pea plant called Spanish Dwarf produces a short plant with white seed. The two varieties are crossed, and the resulting seeds are collected. All of the seeds are white; and when planted, they produce all tall plants. These tall F₁ plants are allowed to self-fertilize. The results for seed color and plant stature in the F₂ generation are as follows:
F₂ Plant Phenotype Number
Blue seed, tall plant. 97
White seed, tall plant 270
Blue seed, short plant 33
White seed, short plant 100
TOTAL 500
Which phenotypes are dominant, and which are recessive? Why?
Table of contents
- 1. Introduction to Genetics51m
- 2. Mendel's Laws of Inheritance3h 37m
- 3. Extensions to Mendelian Inheritance2h 41m
- 4. Genetic Mapping and Linkage2h 28m
- 5. Genetics of Bacteria and Viruses1h 21m
- 6. Chromosomal Variation1h 48m
- 7. DNA and Chromosome Structure56m
- 8. DNA Replication1h 10m
- 9. Mitosis and Meiosis1h 34m
- 10. Transcription1h 0m
- 11. Translation58m
- 12. Gene Regulation in Prokaryotes1h 19m
- 13. Gene Regulation in Eukaryotes44m
- 14. Genetic Control of Development44m
- 15. Genomes and Genomics1h 50m
- 16. Transposable Elements47m
- 17. Mutation, Repair, and Recombination1h 6m
- 18. Molecular Genetic Tools19m
- 19. Cancer Genetics29m
- 20. Quantitative Genetics1h 26m
- 21. Population Genetics50m
- 22. Evolutionary Genetics29m
3. Extensions to Mendelian Inheritance
Variations of Dominance
Struggling with Genetics?
Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
Blood types are an example of what type of dominance?
A
Complete dominance
B
Incomplete dominance
C
Codominance
D
Leaky dominance

1
Understand the concept of dominance in genetics: Dominance refers to the relationship between alleles, where one allele can mask the expression of another in a heterozygous individual.
Review the types of dominance: Complete dominance occurs when the dominant allele completely masks the recessive one. Incomplete dominance results in a blend of traits. Codominance occurs when both alleles are fully expressed in the phenotype. Leaky dominance is not a standard term in classical genetics.
Identify the characteristics of blood types: Human blood types (A, B, AB, O) are determined by the presence or absence of antigens on the surface of red blood cells, specifically the A and B antigens.
Analyze how blood type alleles interact: The A and B alleles are codominant, meaning that if an individual inherits both alleles (genotype AB), both antigens are expressed, resulting in blood type AB.
Conclude that blood types are an example of codominance, as both alleles contribute equally and visibly to the phenotype without blending or masking each other.
Watch next
Master Variations on Dominance with a bite sized video explanation from Kylia
Start learningRelated Videos
Related Practice
Open Question
Variations of Dominance practice set
