3.21 Genetic Probabilities

3.21 predict probabilities of outcomes from monohybrid crosses

P₁ Cross

Parents                         Red petal      x     White Petal
Genotype                          RR           x             rr       (R>r)
Meiosis                       ½ R or ½ R    x       ½ r or ½ r
Random Fertilisation

Male	Female
		r	r
	R	Rr	Rr
	R	Rr	Rr

Genotype offspring       all Rr
Phenotype F₁                all Red
Probability                     100% Red

F₁ Cross

Parents            Red petal         x          Red petal
Genotype        Rr        x          Rr        (R>r)
Meiosis            ½ R or ½ r      x          ½ R or ½ r
Random Fertilisation

Male	Female
		R	r
	R	RR	Rr
	r	Rr	rr

Genotype offspring       RR:2Rr:rr
Phenotype F₂                3 Red : 1 White
Probability                     75% Red, 25% White