Identify the correct sequence of stages in Ross cycle of plasmodium (a) Sporozoite (b) Ookinete (c) Sporozoite (d) Zygote (e) Oocyst

Options

A. `d to b-a-e-c`
B. `c-a-e-b-d`
C. `d to e to b to a to c`
D. `d to b to e to a to c`

Answer

To identify the correct sequence of stages in the Ross cycle of Plasmodium, we need to understand the life cycle of this malaria-causing protozoan, which involves two hosts: humans and female Anopheles mosquitoes. Here’s the step-by-step breakdown of the stages:

1. **Zygote (D)**: The cycle begins in the mosquito's stomach, where male and female gametocytes fuse to form a zygote. This is the first stage in the cycle.

2. **Ookinete (B)**: The zygote then becomes motile and elongated, transforming into an ookinete. This stage is crucial as it allows the parasite to move within the mosquito.

3. **Oocyst (E)**: The ookinete invades the midgut wall of the mosquito and develops into an oocyst. This stage is where the parasite undergoes further development.

4. **Sporozoite (A)**: Once the oocyst matures, it ruptures and releases sporozoites. These sporozoites are the infective form of the parasite.

5. **Sporozoite (C)**: The sporozoites migrate to the mosquito's salivary glands. When the mosquito bites a human, these sporozoites are injected into the human bloodstream, where they can infect liver cells.

Thus, the correct sequence of stages in the Ross cycle of Plasmodium is:
**D (Zygote) → B (Ookinete) → E (Oocyst) → A (Sporozoite) → C (Sporozoite)**.

### Final Answer:
The correct sequence is: **D, B, E, A, C**.