The loops perform intense transcription of heterogenous RNA (precursors of mRNA molecules for ribosomal and histone proteins). Thus each lateral loop is covered by an assymetrical matrix of RNA transcripts; thicker at one end of the loop than other. The number of pairs of loops gradually increases during meiosis till it reaches maximum at diplotene. This  stage may persist for months or years as oocytes build up supply of mRNA required for further development. As meiosis proceeds further number of loops gradually decrease and loops ultimately disappear due to reabsorption into the chromosome or disintegration.

Certain hypothesis regarding loops are that they may be static or dynamic with new loop material spinning out of one side of a chromosome and returning to a condensed on the other side. This is called spinning out or retraction hypothesis.  This hypothesis has been rejected recently through DNA-RNA hybridization studies. The other hypothesis is known as the Master and Slave hypothesis which suggested that each loop pairs and thus chromomere is associated with the activity of many copies of specific genes.  There is a master copy at each chromomere and information is transferred to the slave copies which are matched against it to ensure that all are identical. The master copy does not take part in RNA synthesis, but the slave copy is involved in transcription. Large number of duplicate genes ensures higher level of transcription.

 

Interesting Facts: (Lecture 1,2 and 3)

• If unfolded the DNA in each cell's nucleus would be 2 meters long. Humans have an estimated 100 trillion cells. In other words, if the all the DNA from every cell in a person's body were patched up together they would form a strand of 200 billion kilometers, or more than 1,000 times the distance between Earth and the Sun.
• Genes for the same feature appear in the same locus (place) on each matching pair of chromosomes in every human body cell.
• The 23rd chromosome pair in humans decides what sex you are, and the sex chromosomes are called X and Y.
• In some rare cases people are born with one extra chromosome. Those born with three chromosome 21 have Down's syndrome.
• It takes about 8 hours for one of your cells to completely copy its DNA.
• Human beings share 7% of genes with E. coli bacterium, 21% with worms, 90% with mice and 98% with chimpanzees.