Which stage is responsible for genetic variations and evolution of species ?

Options

A. Diplotene
B. Diakinesis
C. Pachytene
D. Anaphase II

Answer

To answer the question "Which stage is responsible for genetic variations and evolution of species?" we need to analyze the stages of meiosis, particularly focusing on prophase I where genetic variation occurs.

### Step-by-Step Solution:

1. **Understanding Meiosis**: Meiosis is a type of cell division that reduces the chromosome number by half, resulting in four genetically diverse gametes. It consists of two sequential divisions: meiosis I and meiosis II.

2. **Prophase I of Meiosis**: Prophase I is a crucial stage of meiosis that is divided into five sub-stages: Leptotene, Zygotene, Pachytene, Diplotene, and Diakinesis.

3. **Key Sub-stage - Pachytene**: Among these sub-stages, Pachytene is particularly important for genetic variation. During this stage, homologous chromosomes pair up closely in a process called synapsis, forming structures known as bivalents or tetrads.

4. **Crossing Over**: Within the Pachytene stage, crossing over occurs. This is the exchange of genetic material between non-sister chromatids of homologous chromosomes. This recombination of genetic material is a primary source of genetic variation.

5. **Genetic Variation and Evolution**: The genetic variation produced by crossing over during Pachytene contributes to the diversity of traits in a population. This variation is essential for the process of natural selection and evolution of species.

6. **Conclusion**: Therefore, the stage responsible for genetic variations and evolution of species is **Pachytene** during prophase I of meiosis.

### Final Answer:
The stage responsible for genetic variations and evolution of species is **Pachytene**.

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