Meiosis prophase 1: Difference between revisions
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=== Leptotene === | === Leptotene === | ||
Leptotene is the first of fives stages of Prophase 1 and consists of the condensing of the already replicated chromosomes, this procedure continues throughout Prophase 1. The appearance of the chromosomes at this stage of Prophase 1 is likened to 'a string with beads'<ref>Dr. William H. Heidcamp, from 1995 onwards, "Cell Cycles Introduction", available at: http://homepages.gac.edu/~cellab/chpts/chpt11/intro11.html</ref>, these beads are called chromomeres. Each sister chromatid is attached to the nuclear envelope and are so close together that they can be mistaken for only one chromosome | Leptotene is the first of fives stages of Prophase 1 and consists of the condensing of the already replicated [[chromosomes|chromosomes]], this procedure continues throughout Prophase 1. The appearance of the chromosomes at this stage of Prophase 1 is likened to 'a string with beads'<ref>Dr. William H. Heidcamp, from 1995 onwards, "Cell Cycles Introduction", available at: http://homepages.gac.edu/~cellab/chpts/chpt11/intro11.html</ref>, these beads are called chromomeres. Each sister [[chromatid|chromatid]] is attached to the nuclear envelope and are so close together that they can be mistaken for only one chromosome <ref>Macroevolution, "Sub stages of Prophase 1 (Meiosis)", http://www.macroevolution.net/prophase-details.html</ref>.<br> | ||
=== Zygotene === | === Zygotene === | ||
Revision as of 19:05, 28 November 2011
Prophase 1
Prophase 1 of Meiosis is the first stage of meiosis and is defined by five different phases; Leptotene, Zygotene, Pachytene, Diplotene and Diakinesis[1] (in that order). Prophase 1 is essentially the crossing over and recombination of genetic material between non sister chromatids[2] - this results in the genetically unidentical, haploid daughter chromatid cells.
Leptotene
Leptotene is the first of fives stages of Prophase 1 and consists of the condensing of the already replicated chromosomes, this procedure continues throughout Prophase 1. The appearance of the chromosomes at this stage of Prophase 1 is likened to 'a string with beads'[3], these beads are called chromomeres. Each sister chromatid is attached to the nuclear envelope and are so close together that they can be mistaken for only one chromosome [4].
Zygotene
Zygotene is the sub-stage where synpasis between homologous chromosomes begins. These synapsis can form up and down the chromosomes allowing numerous points of contact called 'synaptonemal complex', this can be compared to a zipper structure, due to the coils of chromatin[5].
Pachytene
Once the synapse is formed it is called a bivalent (where a chromatid of one pair is synapsed/attached to the chromatid in a homologous chromosomes[6]) and crossing over can occur. Subsequently the synapses snap completeing the crossing over of the genetic information. As a result the variation in genetic material has been increased significantly, because up and down the chromosome there has been an exchanged of the mother and father's genetic material.
Diplotene
Diakinesis
References
- ↑ Biology online, 26/10/2011, "Prophase 1", Available at: http://www.biology-online.org/dictionary/Prophase_i
- ↑ Biology online, 27/09/2011, “Meiosis” available at: http://www.biology-online.org/dictionary/Meiosis
- ↑ Dr. William H. Heidcamp, from 1995 onwards, "Cell Cycles Introduction", available at: http://homepages.gac.edu/~cellab/chpts/chpt11/intro11.html
- ↑ Macroevolution, "Sub stages of Prophase 1 (Meiosis)", http://www.macroevolution.net/prophase-details.html
- ↑ Macroevolution, "Sub stages of Prophase 1 (Meiosis)", http://www.macroevolution.net/prophase-details.html
- ↑ European informatics institute, 2011, "Pachytene", available at: http://www.ebi.ac.uk/QuickGO/GTerm?id=GO:0000239