The genotype of an individual refers to the combination of alleles (different forms of a gene) that they possess for a particular trait. In this case, the individuals have the genotype AaBb, which means they carry one copy of the A allele and one copy of the a allele, as well as one copy of the B allele and one copy of the b allele.

When two heterozygous individuals with the genotype AaBb are crossed, the offspring have the potential to inherit any combination of alleles from their parents. To determine the probability of a specific genotype, we need to consider the possible combinations of alleles that can be passed on.

- Possible allele combinations from the mother: Aa or a
- Possible allele combinations from the father: Bb or b

Now, let's consider all the possible combinations of alleles that can result in the genotype AaBb:

- AaBb: This can be achieved by inheriting the Aa allele combination from the mother and the Bb allele combination from the father.

The probability of inheriting a particular allele combination from each parent is 1/2, as there are two possible alleles for each gene and the parents are heterozygous. Therefore, the probability of inheriting the Aa allele combination from the mother is 1/2, and the probability of inheriting the Bb allele combination from the father is also 1/2.

To calculate the probability of obtaining the genotype AaBb, we multiply the individual probabilities together:

Probability of inheriting Aa allele combination from the mother = 1/2
Probability of inheriting Bb allele combination from the father = 1/2

Probability of obtaining genotype AaBb = Probability of inheriting Aa allele combination from the mother * Probability of inheriting Bb allele combination from the father
= (1/2) * (1/2)
= 1/4
= 0.25

Therefore, the probability of having a baby with the genotype AaBb is 0.25, or 25%.