Final answer:
In a hybrid plant with heterozygous alleles (Bb), there is a 50 percent chance of obtaining either allele (B or b) in a gamete. This is because alleles segregate during meiosis, leading to an equal chance of transmission to each gamete.
Step-by-step explanation:
In genetic crosses, such as those studied by Mendel, the probability that a particular allele will be in a certain gamete is based on simple chance, akin to flipping a coin. When a plant has two alleles (for example, B and b) for a trait, these alleles segregate during meiosis, with each gamete receiving only one of the two alleles due to the law of segregation.
Using a Punnett square can help to visualize the possible combinations of alleles and their probabilities. If two Bb parents are crossed, the resulting offspring's genotypes could be BB, Bb, bB, and bb. Since Bb and bB are the same, the probability of an offspring being heterozygous like the parents is 50 percent, which comes from two of the four possible gamete combinations (Bb and bB).