Fertilization is complete when –
**Core Concept**
Fertilization is the process by which a sperm fuses with an egg, resulting in the formation of a zygote. This process involves the fusion of the sperm and egg cell membranes, followed by the fusion of their nuclei. The **acrosome** of the sperm plays a crucial role in this process.
**Why the Correct Answer is Right**
The correct answer is not provided, however, fertilization is complete when the sperm nucleus fuses with the egg nucleus, resulting in the formation of a **zygote** with a single set of chromosomes. This process is facilitated by the **acrosome reaction**, which allows the sperm to penetrate the **zona pellucida** of the egg.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because fertilization involves more than just the penetration of the egg by the sperm.
**Option B:** This option is incorrect because the fusion of the sperm and egg membranes is only the first step in the fertilization process.
**Option C:** This option is incorrect because the **corona radiata** is a layer of cells surrounding the egg, but it is not directly involved in the completion of fertilization.
**Option D:** This option is incorrect because the **fertilization tube** is not a recognized term in the context of fertilization.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that fertilization typically occurs in the **ampulla** of the **fallopian tube**.
**Correct Answer:** Correct Answer: D. The sperm nucleus fuses with the egg nucleus.