A dominant allele shows its effect when present in one copy; a recessive allele only shows when two copies are present.
A dominant allele masks the recessive one in heterozygotes, typically because one functional copy produces enough protein. Recessive traits appear only in homozygous recessives. Dominance is a relationship between alleles, not a measure of how healthy or common an allele is.
Capital letters represent dominant alleles and lower-case recessive.
A dominant allele shows its effect when present in one copy; a recessive allele only shows when two copies are present.
Dominant and Recessive is one of the 54 topics in Genetics. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Homozygous and Heterozygous, Codominance, Inherited Disorders.
Cystic fibrosis is recessive; Huntington's disease is dominant.
Dominant and Recessive is a Beginner topic, so no earlier topic is required. Other Beginner topics in Genetics that pair well with it include Heredity, Gene, Allele.
The closest topics to Dominant and Recessive are Homozygous and Heterozygous, Codominance, Inherited Disorders, Incomplete Dominance. Comparing them side by side is a good way to see how the ideas connect.
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Dominant and Recessive. To practise the whole of Genetics, use the Genetics quiz.
Dominant and Recessive: A dominant allele shows its effect when present in one copy; a recessive allele only shows when two copies are present. Homozygous and Heterozygous: Homozygous means two identical alleles for a gene; heterozygous means two different alleles. Read both side by side and note what each one explains.
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Homozygous and Heterozygous and explain the difference aloud. Finally, take the Genetics quiz and come back to this page for any question you miss.
Homozygous means two identical alleles for a gene; heterozygous means two different alleles.
🧬 GeneticsBoth alleles are fully expressed in the heterozygote, as in the AB blood type.
🧬 GeneticsConditions caused by faulty genes passed through families, such as cystic fibrosis and sickle cell disease.
🧬 GeneticsThe heterozygote shows an intermediate phenotype, such as pink flowers from red and white parents.
🧬 Genetics