The main difference between leptotene and zygotene is that chromosomes are visible and condense under an electron microscope in leptotene, whereas synapsis between homologous chromosomes occurs in the zygotene stage.
Leptotene and zygotene are two sub-stages of prophase 1 of meiosis. Chromosomes become thicker and visible under the microscope.
Key Areas Covered
1. What is Leptotene
– Definition, Features, Function
2. What is Zygotene
– Definition, Features, Function
3. Similarities Between Leptotene and Zygotene
– Outline of Common Features
4. Difference Between Leptotene and Zygotene
– Comparison of Key Differences
5. FAQ: Leptotene and Zygotene
– Answers to frequently asked questions
Key Terms
Leptotene, Leptonema, Zygotene, Zygonema
What is Leptotene
Leptotene is the first sub-stage of prophase 1. It occurs in the meiosis 1. Another name for leptotene is leptonema. Cells undergo meiosis to produce gametes. They undergo chromosome duplication during interphase. The interphase is the initial or growth phase of the cell cycle in eukaryotes. Before entering the cell division, the cell prepares for its division by uptaking all required nutrients into the cell, protein synthesis, and replication of DNA. Interphase accounts for about 90% of the total time of the cell cycle. Further, the duplicated chromosomes contain two sister chromatids. Here, chromatids condense from diffuse chromatin, forming thin, long strands. They are more visible within the nucleoplasm.
Figure 1: Leptotene
Furthermore, chromosomes attach themselves to the inner membrane of the nuclear envelope by their telomeres. The aggregation of telomeres occurs in a nuclear envelope sector. Therefore, it forms a meiotic bouquet. Also, the formation of lateral elements of the synaptonemal complex occurs.
What is Zygotene
Zygotene is the second sub-stage of prophase 1 that occurs in meiosis 1. Zygonema is another name for zygotene. It contains paired threads. A much more stable pairing of homologous chromosomes occurs in this stage. They occur ~100 nm closer. Further, the synapsis of homologous chromosomes occurs in a zipper-like fashion. It starts from a recombination nodule.
Figure 2: Zygotene
Similarities Between Leptotene and Zygotene
- Leptotene and zygotene are two sub-stages of prophase 1.
- Thicker and visible chromosomes are the characteristic features of prophase 1.
- They occur in the meiosis.
Difference Between Leptotene and Zygotene
Definition
Leptotene refers to the first stage of the prophase of meiosis, during which each chromosome becomes visible as two fine threads (chromatids). At the same time, zygotene refers to zygotene refers to the second stage of the prophase of meiosis, following leptotene, during which homologous chromosomes begin to pair.
Stage
Leptotene is the first stage of prophase 1, while zygotene is the second stage of prophase 1.
Follows
Leptotene follows interphase, while zygotene follows leptotene.
Function
Chromosomes are visible and condense under an electron microscope in leptotene, while synapsis between homologous chromosomes occurs in the zygotene stage.
FAQ: Leptotene and Zygotene
What is the difference between zygotene, pachytene, and diplotene?
Zygotene, pachytene, and diplotene are three stages of prophase 1. Chromosomes align and prepare for recombination. Crossing over occurs between the chromatids in the tetrad in zygotene. The separation of chromosomes begins in the pachytene stage. Also, the breakdown of chiasmata occurs, and chromosome pairs move apart in the diplotene stage.
What happens at the leptotene stage?
Chromosomes become visible, forming thread-like structures in the leptotene stage. Bead-like structures called chromomeres are visible in the leptotene stage. The bouquet stage is another name for the leptotene stage due to the specific alignment of chromosomes in the nucleus.
What is the order of leptotene zygotene?
Leptotene, zygotene, pachytene, diplotene and diakinesis are the five stages of prophase 1. They occur in meiosis 1, one of the two stages of cell division. Meiosis is the process of reducing the number of chromosomes in gametes.
Conclusion
In brief, leptotene and zygotene are two sub-stages of prophase 1. They occur in meiosis 1. Leptotene is the first stage of prophase 1. In the leptotene, chromosomes are visible and condense under the electron microscope. In comparison, zygotene is the second stage of prophase 1. It follows leptotene. Synapsis between homologous chromosomes occurs in the zygotene stage. Therefore, the main difference between leptotene and zygotene is their function.
References:
- Meiosis I: Definition, examples, diagrams. Toppr Ask. (n.d.).
Image Courtesy:
- “Meiosis Overview new” By Rdbickel – Own Work (CC-BY SA 4.0) via Commons Wikimedia
- “Synaptonemal Complex” By Daniel Wells – Own Work (CC-BY SA 4.0) via Commons Wikimedia
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