3.21) Genetic Probability

Predict probabilities of outcomes from monohybrid crosses

Monohybrid - a hybrid that is heterozygous with respect to a specified gene

Generation 1:

Red (RR) x White (rr)

Red is dominant to white. 

---> Meiosis

The alleles are being separated. The gamete would contain one one of the two alleles with equal chance. 

Which means the gametes of red petals will be separated into (1/2)R and (1/2)R. The white petals would be (1/2) r and (1/2) r.

We then considered random fertilization by drawing table to illustrate to possible phenotypes and genotypes of the offsprings through Punnett square (Mendel's diagram). 

In this example, the genotype would all be Rr.

So the phenotype would ALL be red. 

So the probability would be 100% that you would have a red offspring. 

Generation 2:

Now we try to cross heterozygous parents (Rr) and (Rr)

We have…

25% of RR

50% of Rr

25% of rr

Genotype ratio…

RR:Rr:rr = 1:2:1

Phenotype ratio…

Red:White - 3:1

They are chances and probability. It depends on which pollen grain fertilizes with which ovule.