Inheritance of One Gene (Monohybrid Cross)
Study of inheritance patterns involving a single pair of contrasting characters, analyzing F1 and F2 generations and their phenotypic and genotypic ratios.
What is Inheritance of One Gene (Monohybrid Cross)?
A genetic cross between two individuals that are heterozygous for one gene, or a cross between two individuals that differ in only one trait.
Key formula / rule: Phenotypic Ratio (F2)
Key points
- Explain the concept of a monohybrid cross.
- Predict the phenotypic and genotypic ratios of offspring from monohybrid crosses.
- Apply Mendel's Law of Segregation to explain inheritance patterns.
- Differentiate between dominant and recessive traits.
Common exam trap
Confusing genotype with phenotype.
Definitions
- Term
Monohybrid Cross
- Meaning
A genetic cross between two individuals that are heterozygous for one gene, or a cross between two individuals that differ in only one trait.
- Term
Allele
- Meaning
One of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.
- Term
Homozygous
- Meaning
Having identical alleles for a particular gene (e.g., TT or tt).
- Term
Heterozygous
- Meaning
Having two different alleles for a particular gene (e.g., Tt).
- Term
Phenotype
- Meaning
The observable physical or biochemical characteristics of an organism, as determined by both genetic makeup and environmental influences.
- Term
Genotype
- Meaning
The genetic constitution of an organism, referring to the specific alleles it possesses for a particular gene or set of genes.
- Term
Law of Segregation
- Meaning
The principle, formulated by Gregor Mendel, stating that the two alleles for each trait separate during gamete formation and unite randomly during fertilization.
Learning objectives
Explain the concept of a monohybrid cross.
Predict the phenotypic and genotypic ratios of offspring from monohybrid crosses.
Apply Mendel's Law of Segregation to explain inheritance patterns.
Differentiate between dominant and recessive traits.
Construct and interpret Punnett squares for monohybrid crosses.
Formulae
- Name
Phenotypic Ratio (F2)
- Note
Observed in a monohybrid cross between heterozygous parents (e.g., Tt x Tt).
- Expression
3 Dominant : 1 Recessive
- Name
Genotypic Ratio (F2)
- Note
Observed in a monohybrid cross between heterozygous parents (e.g., Tt x Tt).
- Expression
1 Homozygous Dominant : 2 Heterozygous : 1 Homozygous Recessive
Prerequisites
Basic understanding of genetics and heredity.
Knowledge of cell division (mitosis and meiosis).
Familiarity with terms like gene, allele, trait, character, homozygous, heterozygous.
Common mistakes
Confusing genotype with phenotype.
Incorrectly applying ratios to small sample sizes.
Assuming that the F1 generation's phenotype will always be the only one present in F2.
Not understanding the concept of alleles and their segregation.
Forgetting to consider both phenotypic and genotypic ratios.
Keywords
Monohybrid Cross
Mendel
Law of Segregation
Alleles
Homozygous
Heterozygous
Phenotype
Genotype
F1 Generation
F2 Generation
Punnett Square
Dominant
Recessive
Practice preview
A geneticist performs a monohybrid cross between two pea plants, both heterozygous for seed color (Yy x Yy), where yellow (Y) is dominant over green (y). If 800 seeds are produced in the F2 generation, how many of these …
hard
In Mendel's monohybrid cross for tall and dwarf pea plants, what was observed in the F1 generation?…
easy
What is the phenotypic ratio observed in the F2 generation of a monohybrid cross?…
easy