Question

In a cross between two varieties of corn, \(g l_{1} g l_{1} W s_{3} W s_{3}\) (egg parent) \(\times G l_{1} G l_{1} w s_{3} w s_{3}\) (pollen parent), a triploid offspring was produced with the genetic constitution \(G l_{1} G l_{1} g l_{1} W s_{3} w s_{3} w s_{3}\) From which parent, egg or pollen, did the \(2 n\) gamete originate? Is another explanation possible? Explain.

Short answer

Answer: The 2n gamete originated from the pollen parent.

Step-by-step solution

Identify the parent's genetic constitution

The genetic constitution of the parents is given as: Egg parent: \(g l_{1} g l_{1} W s_{3} W s_{3}\) Pollen parent: \(G l_{1} G l_{1} w s_{3} w s_{3}\)

Identify the offspring's genetic constitution

The genetic constitution of the offspring is given as: \(G l_{1} G l_{1} g l_{1} W s_{3} w s_{3} w s_{3}\)

Compare the offspring's genetics with the parent plants

Now, let's compare the offspring's genetics to that of the parent plants. In the offspring, for the \(G l_{1}\) and \(g l_{1}\) genes, there are two copies of the dominant gene (\(G l_{1}\)) and one copy of the recessive gene (\(g l_{1}\)). The pollen parent has two copies of the dominant gene, while the egg parent has only recessive genes for this trait. This suggests that the 2n gamete with the extra copy originated from the pollen parent for this gene. For the \(W s_{3}\) and \(w s_{3}\) genes, the offspring has one copy of the dominant gene (\(W s_{3}\)) and two copies of the recessive gene (\(w s_{3}\)). In this case, the egg parent has two copies of the dominant gene, while the pollen parent has only recessive genes for this trait. This suggests that the 2n gamete with the extra copy originated from the pollen parent for this gene as well.

Determine the origin of the 2n gamete

Since the offspring has extra copies of both dominant and recessive genes found in the pollen parent, we can conclude that the 2n gamete originated from the pollen parent.

Consider other possible explanations

The given information explains the genetic constitution of the offspring, so there is no need to consider other explanations. The conclusion that the 2n gamete originated from the pollen parent is consistent with the given information.