Study Notes
Monohybrid inheritance involves the inheritance of a single characteristic controlled by different alleles of a gene. It helps predict the outcome of offspring traits based on parental genotypes.
- Genotype — the genetic makeup of an organism in terms of the alleles present. Example: Tt or GG
- Phenotype — the physical or other features of an organism due to both its genotype and its environment. Example: tall plant or green seed
- Homozygous — having two identical alleles of a particular gene. Example: TT or gg
- Heterozygous — having two different alleles of a particular gene. Example: Tt or Gg
- Dominant — an allele that is expressed if it is present. Example: T or G
- Recessive — an allele that is only expressed when there is no dominant allele of the gene present. Example: t or g
- Allele — different form of a gene. Example: Blue colour allele or Brown colour allele
Exam Tips
Key Definitions to Remember
- Genotype: genetic makeup of an organism
- Phenotype: physical characteristics due to genotype and environment
- Homozygous: two identical alleles
- Heterozygous: two different alleles
- Dominant: allele expressed when present
- Recessive: allele expressed only without dominant allele
Common Confusions
- Mixing up genotype and phenotype
- Confusing homozygous with heterozygous
Typical Exam Questions
- What is the genotype of a homozygous dominant organism? Answer: BB
- How does a recessive allele express itself? Answer: Only when no dominant allele is present
- What is the phenotype ratio in a monohybrid cross between two heterozygous parents? Answer: 3:1
What Examiners Usually Test
- Understanding of genotype and phenotype differences
- Ability to predict offspring traits using monohybrid crosses
- Interpretation of family pedigrees