Meiosis I - Reductional Cell Division

Sexual propagation in living beings happens through the combination of male and female gametes, the sperm and the egg individually. Gametes are haploid in nature, i.e., they contain just a large portion of the quantity of chromosomes. This hereditary substance makes them unique in relation to other body cells. Meiosis prompts the arrangement of haploid cells. Let us have a point by point take a glimpse at meiosis 1 and the various stages and periods of meiosis 1. Mitotic cell division is equational in nature while meiosis is a decreasing division. The notable highlights of meiotic division that make it not quite the same as mitosis are as per the following:- 

• It happens in two phases of the atomic and cell division as Meiosis I and Meiosis II. DNA replication happens, nonetheless, just a single time. 

• It includes the matching of homologous chromosomes and recombination between them. 

• Four haploid girl cells are delivered toward the end, dissimilar to two diploid little girl cells in mitosis. 

• Meiosis 1 isolates the pair of homologous chromosomes and lessens the diploid cell to haploid. It is isolated into a few phases that incorporate prophase, metaphase, anaphase and telophase.

Meiosis 1 Stages 

The various phases of meiosis 1 can be clarified by the accompanying stages : 

• Prophase 1 

• Metaphase 1 

• Anaphase 1 

• Telophase 

Phases of Meiosis 1 

The means paving the way to meiosis are like those of mitosis – the centrioles and chromosomes are repeated. The measure of DNA in the cell has multiplied, and the ploidy of the cell continues as before as in the past, at 2n. In meiosis I, the stages are practically equivalent to mitosis: prophase I, metaphase I, anaphase I, and telophase I (underneath figure). Meiosis I continues legitimately to meiosis II without experiencing interphase.

Meiosis I is novel in that hereditary assorted variety is produced through traverse and irregular situating of homologous chromosomes (bivalent chromosomes). What's more, in meiosis I, the chromosomal number is decreased from diploid (2n) to haploid (n) during this procedure. (See figure underneath, where meiosis I starts with a diploid (2n = 4) cell and finishes with two haploid (n = 2) cells.) In people (2n = 46), who have 23 sets of chromosomes, the quantity of chromosomes is diminished considerably toward the finish of meiosis I (n = 23).

Meiosis 1 Prophase 1 

Prophase I is longer than the mitotic prophase and is additionally partitioned into 5 substages.

• Leptotene 

• Zygotene 

• Pachytene 

• Diplotene 

• Diakinesis 

The chromosomes start to consolidate and accomplish a reduced structure during leptotene. In zygotene, the blending of homologous chromosomes begins a procedure known as chromosome synapsis, joined by the arrangement of an unpredictable structure called synaptonemal complex. A couple of synapsed homologous chromosomes shapes a complex known as bivalent or quadruplicate.

At the pachytene stage, traverse of non-sister chromatids of homologous chromosomes happens at the recombination knobs. The chromosomes stay connected at the destinations of traverse. 

Diplotene denotes the disintegration of the synaptonemal complex and partition of the homologous chromosomes of the bivalents with the exception of at the destinations of traverse. The X-molded structures shaped during detachment are known as chiasmata.

Diakinesis is set apart by the end of chiasmata and gathering of the meiotic axle to isolate the homologous chromosomes. The nucleolus vanishes and the atomic envelope separates.

Meiosis 1 Metaphase 1 

The bivalents adjust at the tropical plate and microtubules from the contrary posts join to the sets of homologous chromosomes.

Meiosis 1 Anaphase 1 

The two chromosomes of each bivalent discrete and move to the furthest edges of the cells. The sister chromatids are joined to one another.

Meiosis 1 Telophase 1 

The atomic layer returns and is trailed by cytokinesis. This offers access to a dyad of cells. 

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