Synaptonemal complex

Details about Synaptonemal complex

1. Synaptonemal Complex & Lampbrush Chromosome By S.Ramya I M.Sc Microbiology

2. Synaptonemal Complex

3. Synaptonemal complex The synaptonemal complex (SC) is a protein structure that forms between homologous chromosomes (two pairs of sister chromatids ) during meiosis and is thought to mediate chromosome pairing, synapsis , and recombination . The paired homologous chromosomes are joined by a protein containing frame work called Synaptonemal complex .

4. Synapsis The first unique feature of meiosis happens early during the first nuclear division. Following chromosome replication, homologous chromosomes, or homologues pair all along their length. The process of forming these complexes of homologous chromosomes is called synapsis

5. Synaptonemal complex The synaptonemal complex was described by Montrose J. Moses in 1956 in primary spermatocytes of crayfish and by D. Fawcett in spermatocytes of pigeon, cat and man . The synaptonemal complex is a tripartite structure consisting of two parallel lateral regions and a central element . Three specific components of the synaptonemal complex have been characterized: SC protein-1 (SYCP1), SC protein-2 (SYCP2), and SC protein-3 (SYCP3) .

6. A Mature Synaptonemal Complex

7. Lampbrush Chromosome

8. Lampbrush chromosome First observed by Flemming in 1882. The name lampbrush was given by Ruckert in 1892. It is the largest chromosome known and is found in the amphibian oocytes (immature eggs). Also seen in diplotene in oocytes of fish, birds, reptiles and some invertebrates .

9. Lampbrush chromosome Lampbrush chromosomes occur during the diplotene stage of meiosis I . They are meiotic bivalents , each consisting of two pairs of sister chromatids . Lampbrush chromosomes are so called because the chromosomes seem to have a chromomeric pattern with loops projecting in pair from majority of chromosomes and they appear like the brushes , that were used for cleaning glass chimneys of kerosene lamps.

10. Lampbrush chromosomes are clearly visible even in the light microscope.

11. The meiotically paired chromosomes in growing amphibian oocytes are highly active in gene expression, and they form unusually stiff and extended chromatin loops. Experiments demonstrate that most of the genes present in the DNA loops are being actively expressed.