Lampbrush Chromosomes (Ruckert, 1882)

 

 

1. Occurrence: Found in oocytes of invertebrates and vertebrates, except mammals.
2. Observation Stage: Distinctly observed during the prolonged diplotene stage of prophase I.
3. Chromomere Formation: A pair of lateral loops is formed from the majority of chromomeres.
4. Loop Pairs: One to nine pairs of loops can originate from a single chromomere.
5. Length: Ranges from 800 to 1000 μm.
6. Loop Size: Loops vary in size from 9.5 μm to 200 μm.
7. Loop Dynamics: Loops are slowly withdrawn at metaphase.
8. Chromatid Structure: Each loop represents a single chromatid, which is a fully extended DNA double helix.
9. Function: Sites for RNA synthesis.
10. Primary Function: To produce large quantities of protein and RNA, which are stored in eggs.
11. Gene Transcripts: Gene transcripts are stored in an inactive but stable form and become active only after fertilization.