This deep dive covers Key Terms for Genetics within Genetic Inheritance for GCSE Biology. Genetic inheritance patterns, alleles, and inheritance diagrams It is section 1 of 9 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Key Terms for Genetics
The Bossy vs Shy Allele
Dominant alleles are bossy — if one is present, it shows. Capital letter (B).
Recessive alleles are shy — only show up when there's no bossy allele around. Lowercase (b).
Bb = Brown eyes (bossy B wins). bb = Blue eyes (both shy, so blue shows).
| Term | Meaning |
|---|---|
| Dominant | Allele that is always expressed when present (shown with CAPITAL letter, e.g., B) |
| Recessive | Allele only expressed when there's no dominant allele (lowercase, e.g., b) |
| Homozygous | Two identical alleles (BB or bb) |
| Heterozygous | Two different alleles (Bb) |
| Genotype | The alleles an organism has (e.g., Bb) |
| Phenotype | The physical characteristic (e.g., brown eyes) |
Practice questions for Genetic Inheritance
What is the term for an allele that is always expressed when present?
What is the purpose of a Punnett square in genetic inheritance?
Quick recall flashcards
What is a dominant allele?
An allele that is always expressed in the phenotype, even if only one copy is present. Represented by a capital letter (e.g. B). Think of it as the 'bossy' allele.
What is a recessive allele?
An allele that is only expressed when two copies are present (homozygous recessive). Represented by a lower-case letter (e.g. b). It is 'hidden' by a dominant allele.