Are the ratios obtained in a dihybrid cross always the same? Explain.
No, the ratios obtained in a dihybrid cross are not always the same. The ratios obtained depend on the genotype of the parental plants involved in the cross.
In a dihybrid cross, two traits controlled by different gene pairs are crossed. Each gene pair segregates independently during gamete formation, meaning that the alleles for each trait separate randomly.
When two heterozygous (hybrid) individuals for both traits are crossed, the possible genotypes of the offspring are formed by combining the alleles of the parental plants. The four possible combinations for each gene pair result in four phenotypic combinations for the two traits.
The expected phenotypic ratios in the offspring vary depending on the mode of inheritance of each trait. If both traits exhibit Mendelian inheritance, where dominance and recessiveness patterns are observed, a 9:3:3:1 ratio is expected. This ratio represents 9 offspring with both dominant traits, 3 offspring with each of the two dominant traits and a recessive trait, 1 offspring with both recessive traits.
However, if the traits are genetically linked, meaning that they are located on the same chromosome and tend to be inherited together, the expected ratios can deviate from the classic Mendelian ratios. In this case, a modified ratio reflecting the linkage between the traits would be observed.
To determine the actual ratios obtained in a dihybrid cross, the genotypes of the parental plants need to be known, and a Punnett square or a probability table can be used to calculate the expected phenotypic ratios. By crossing a large number of plants, the observed ratios can be compared to the expected ratios to assess the validity of the results and to detect any deviations or inconsistencies.