Other Pages Facts Lampbrush chromosomes occur in a limited phase of meiosis during oogenesis in amphibian oocytes. An identical pattern of twinned loops occurs on both pairs of sister chromatids. Loops show a gradual increase of electron density from the chromomere around the loop and back to the chromomere. The average length of loops corresponds to the average length of RNA transcripts in these oocytes, but is much longer than the average length of RNA transcribed in somatic cells.
Loops are transcription units .
They are longer than in somatic cells due to failure to terminate transcription at the same positions. Loops in lampbrush chromosomes suggest that metaphase chromosomes may result from interphase chromosomes by the formation of loops, followed by the aggregation of chromomeres. Lampbrush chromosomes are thought to assist in fulfilling the high demand for transcripts during amphibian oogenesis . Lampbrush chromosomes are also present during development of other animals, but have been most studied in amphibians. Lampbrush chromosomes lack histone H1.