Which stage of meiotic prophase shows terminalisation of chiasmata as its distinctive feature
Pachytene
Leptotene
Zygotene
Diakinesis
The Correct Option is D
Solution and Explanation
To answer the question about the stage of meiotic prophase that shows terminalisation of chiasmata as its distinctive feature, we need to understand the phases of meiotic prophase and the events occurring in each phase.
Meiotic prophase is a critical phase in meiosis composed of five stages:
- Leptotene: Chromosomes start to condense and become visible as long, thin threads.
- Zygotene: Homologous chromosomes pair up through a process called synapsis to form bivalents.
- Pachytene: Crossing over occurs between homologous chromosomes where genetic material is exchanged, but chiasmata are not yet visible.
- Diplotene: Synapsis ends, and homologous chromosomes begin to separate but remain attached at the chiasmata, where crossing over has happened.
- Diakinesis: This is the stage where chiasmata move towards the ends (terminalisation), making it the distinctive feature of this stage. Chromosomes are fully condensed and prepared for metaphase I.
The correct answer to the question is Diakinesis, as terminalisation of chiasmata is the key characteristic of this stage.
Let's justify why the other options do not show terminalisation:
- Pachytene: This stage involves crossing over, but the chiasmata themselves are not yet moving towards the chromosome ends.
- Leptotene: This is the initial stage where chromosomes condense, and no chiasmata are visible.
- Zygotene: Homologous chromosomes pair, but no chiasmata or terminalisation is observed here.
Therefore, the answer to the question is Diakinesis.
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Concepts Used:
Meiosis
Meiosis is a process in which a single cell, a diploid cell, undergoes division twice to produce four haploid daughter cells, and the cells produced are known as the sex cells or gametes (sperms in males and egg in females). It contains half of the original amount of genetic information. The haploids only have half the number of chromosomes of the parent cell.
Features of Meiosis:
- It results in the formation of four daughter cells in each cycle of cell division.
- The daughter cells are identical to the mother cell in shape and size but different in chromosome number.
- The daughter cells are haploid.
- Recombination and segregation take place in meiosis.
- The process occurs in the reproductive organs and results in the formation of gametes.
- The process is divided into two types-Meiosis-I reduces the chromosome number to half and is known as reductional division. Meiosis-II is just like the mitotic division.
Phases of Meiosis
Meiosis can be divided into nine stages. The process is usually divided into two parts. The first time a cell divides (meiosis I) and the second time it divides (meiosis II). The phases are as follows –
Meiosis 1 Stages
The different stages of meiosis 1 can be explained by the following phases :
- Prophase 1
- Metaphase 1
- Anaphase 1
- Telophase 1
Meiosis 2 Stages
The different stages of meiosis 1 can be explained by the following phases :
- Prophase 2
- Metaphase 2
- Anaphase 2
- Telophase 2