Final answer:
The two possible linked allele configurations for gametes are AB and ab, which occur in a 1:1 ratio. Recombination can sometimes produce Ab and aB configurations, leading to genetic diversity.
Step-by-step explanation:
When two genes, A and B, are linked on the same chromosome, their alleles tend to be inherited together during meiosis due to their physical proximity. In the original parental cross (P0), we have a parent that is homozygous dominant (AB/AB) and another that is homozygous recessive (ab/ab). The heterozygous individual (AaBb) formed from this cross, when producing gametes, will mostly produce gametes that show the original parental configurations (AB or ab) in a 1:1 ratio.
However, due to the possibility of recombination during meiosis, a smaller proportion of gametes can contain recombinant allele configurations (Ab or aB), leading to genetic diversity. This phenomenon was observed by Morgan and his colleagues through experimental crosses. So, while the two possible linked allele configurations for gametes are AB and ab, occasional recombination events can generate Ab and aB configurations as well.