Summary OCR A-Level Biology 6.2.2 Monogenic Inheritance

Monogenic Inheritance
Monohybrid Cross
 Monogenic = determined by a single gene
 Results in a 3:1 ratio
 Example: Dominant = T Recessive = t
 Homozygous Dominant = TT Heterozygous = Tt Homozygous Recessive = tt
 Punnett Squares:


Homozygous D x Homozygous
Parent Phenotype Heterozygous x Heterozygous R
Parent Genotype Tt x Tt TT x tt
Parent Gametes T t T t T T t t
Monohybrid Cross T t t t
T TT Tt T Tt Tt
t Tt tt T Tt Tt
Ratio 3:1 All Dominant

Parent Phenotype Homozygous D x Heterozygous Homozygous R x Heterozygous
Parent Genotype TT x Tt tt x Tt
Parent Gametes T T T t t t T t
Monohybrid Cross T t T t
T TT Tt t Tt tt
T TT Tt t Tt tt
All Dominant 1:1