Unit 11 assignment 3
Monohybrid inheritance between 2 heterozygous individuals
● Monohybrid inheritance describes the inheritance of a single trait that is determined
by two alleles (one from each parent). Each parent in a hybrid involving two
heterozygous individuals carries two distinct alleles, one recessive and one
dominant.
E.g. height of plant where tall (T) is dominant over short (t)
Genotypes: TT, homozygous dominant (25% chance)
Tt, heterozygous (50% chance)
tt, homozygous recessive (25% chance)
Phenotypes: Tall (TT, Tt): 75% chance
Short (tt): 25% chance
Ratio: 3:1
Monohybrid inheritance for co-dominant allele
● When two alleles, both of which are equally expressed in the heterozygous state,
regulate a single trait, this is known as monohybrid inheritance involving codominant
alleles. Similar to the normal dominant-recessive relationship, co-dominant alleles
produce a phenotype in which both alleles influence the characteristics of the
organism
E.g. flower species where the flowers colour is determined by two codominant alleles red (R)
and white (W)
Genotypes: RR, homozygous (25% chance)
RW, heterozygous (50% chance)
WW, homozygous (25% chance)
Phenotypes: Red (RR), 25% chance
Red and white (RW), 50% chance
White (WW), 25% chance
Ratio: 1:2:1
Dihybrid inheritance between 2 heterozygous individuals (9:3:3:1)
Monohybrid inheritance between 2 heterozygous individuals
● Monohybrid inheritance describes the inheritance of a single trait that is determined
by two alleles (one from each parent). Each parent in a hybrid involving two
heterozygous individuals carries two distinct alleles, one recessive and one
dominant.
E.g. height of plant where tall (T) is dominant over short (t)
Genotypes: TT, homozygous dominant (25% chance)
Tt, heterozygous (50% chance)
tt, homozygous recessive (25% chance)
Phenotypes: Tall (TT, Tt): 75% chance
Short (tt): 25% chance
Ratio: 3:1
Monohybrid inheritance for co-dominant allele
● When two alleles, both of which are equally expressed in the heterozygous state,
regulate a single trait, this is known as monohybrid inheritance involving codominant
alleles. Similar to the normal dominant-recessive relationship, co-dominant alleles
produce a phenotype in which both alleles influence the characteristics of the
organism
E.g. flower species where the flowers colour is determined by two codominant alleles red (R)
and white (W)
Genotypes: RR, homozygous (25% chance)
RW, heterozygous (50% chance)
WW, homozygous (25% chance)
Phenotypes: Red (RR), 25% chance
Red and white (RW), 50% chance
White (WW), 25% chance
Ratio: 1:2:1
Dihybrid inheritance between 2 heterozygous individuals (9:3:3:1)
