VIDEO DESCRIPTION:

Play, download and edit the free video Spliceosome animation.

Schematic of the action of the spliceosome.

Philip Sharp won the 1993 Nobel prize in biology for his 1977 discovery that the genetic code in RNA was spliced together, not just a simple 'mindless' transcription from DNA. How this splicing happened was a mystery for many years, and the mystery was deepened after 2000 when human DNA was sequenced and it was found that 90% of the genome is non-coding (aka “junk”). This fed into the unanticipated discovery of an active protein complex in the nucleus of every cell, hiding in plain sight, subsequently dubbed the “Spliceosome”. This complex is composed of 200 active proteins, all with different functions. It is somewhat structurally similar to the Ribosome (hence the likeness of the names), another protein complex which manufactures Amino Acids (the building blocks of proteins) based on code supplied by RNA. The word ‘complex’ can be more understandable in this case if we just think of it as: 'a machine which makes things (proteins) according to printed instructions.'

It was further discovered that the Spliceosome tears into RNA after it has copied a string of letters from DNA (think of the mould-copying of a section of a recording disk in the old days). Using crispr scissors, the Spliceosome cuts out the junk (technically called introns) and then loops together the good bits (technically: exons) while frequently rearranging those good bits into a better order than they were in the original DNA string. Once that is done, the RNA is free to leave the cell’s nucleus, wiggling through the nucleic membrane, and once it is in the body of the cell (the cytoplasm) it is pounced on by ribosomes, who quickly use the spliceosome-edited information to manufacture amino acids, which eventually self-organize into proteins.

Every cell in our bodies - in fact the bodies of all creatures on earth other than bacteria - has this furious activity going on inside it. DNA has consequently been somewhat demoted to what it really is: a crystalline database of information, largely inert.

“DNA is a dead molecule, among the most nonreactive, chemically inert molecules in the living world. That is why it can be recovered in good enough shape to determine its sequence from mummies, from mastodons frozen tens of thousands of years ago, and even, under the right circumstances, from twenty-million-year-old fossil plants … DNA has no power to reproduce itself. Rather it is produced out of elementary materials by a complex cellular machinery of proteins. While it is often said that DNA produces proteins, in fact proteins (enzymes) produce DNA … Not only is DNA incapable of making copies of itself, aided or unaided, but it is incapable of ‘making’ anything else”

- Richard Lewontin (Harvard Geneticist)

The Spliceosome, however, is buzzing with activity, pruning and structuring coherent - and greatly variable - “print masters" from the largely incoherent (junk-filled) information stored in DNA.

This is relatively new information (emerging over the last few decades or so) and hasn’t yet percolated out of the higher reaches of biology into mainstream consciousness.

The still-unresolved question is: how does the Spliceosome know how to do what it does?

Download, play and edit free videos and free audios from Spliceosome animation using RedcoolMedia.net web apps