Final answer:
In monohybrid crosses, the genotypes of offspring can be predicted based on parental contributions of alleles. For offspring genotype TT and tt, the parents are Tt and Tt. For TT and Tt, the parents are TT and Tt, and for tt and tt the parents are tt and tt. These predictions are based on Mendelian inheritance and can be illustrated using a Punnett square.
Step-by-step explanation:
To determine the genotypes of the parents in a monohybrid cross, one must consider which combinations of alleles can produce the predicted offspring genotypes. A monohybrid cross involves the inheritance of a single trait.
- For offspring genotypes TT and tt, the parents must be Tt and Tt. Each parent contributes one dominant (T) or recessive (t) allele, allowing both homozygous dominant (TT) and homozygous recessive (tt) offspring to occur.
- For offspring genotypes Tt and Tt, the parents must also be Tt and Tt, as this signifies a typical Mendelian 3:1 ratio in a monohybrid cross between two heterozygotes.
- For offspring genotypes TT and Tt, one parent must be homozygous dominant (TT) and the other heterozygous (Tt). This is because the only way to get a TT offspring is if one parent can only give a dominant allele (T).
- For offspring genotypes tt and tt, the parents must both be homozygous recessive (tt). This combination will only produce recessive offspring.
The use of a Punnett square can illustrate the expected offspring genotypes from the genetic crosses. A Punnett square shows all the possible combinations of parental alleles and the genotypes of resulting offspring.