Which stage of meiotic prophase shows terminalisation of chiasmata as its distinctive feature?

The correct option is Diakinesis.

Explanation:
Prophase I of meiosis I is a complex and extended phase that is divided into five distinct stages based on chromosomal behavior: Leptotene, Zygotene, Pachytene, Diplotene, and Diakinesis.

Here is a step-by-step breakdown of these stages, highlighting their key characteristics:

1. Leptotene: During this initial stage, chromosomes become gradually visible under the light microscope as they undergo condensation.

2. Zygotene: In this stage, homologous chromosomes start pairing up, a process called synapsis. The paired chromosomes are called bivalents or tetrads.

3. Pachytene: This stage is characterized by crossing over, where non-sister chromatids of homologous chromosomes exchange genetic material. Recombination nodules become visible, marking the sites where crossing over occurs.

4. Diplotene: The synaptonemal complex dissolves, and the homologous chromosomes start separating from each other except at the sites of crossovers. These X-shaped points of contact are called chiasmata.

5. Diakinesis: This is the final stage of meiotic prophase I. Its distinctive feature is the terminalisation of chiasmata, which means the chiasmata slip or shift towards the ends (telomeres) of the chromosomes, eventually resolving. By the end of diakinesis, the nucleolus disappears, the nuclear envelope breaks down, and the meiotic spindle is fully assembled to prepare the chromosomes for metaphase I.