What's New

Corrected the discussion of the pyrophosphatase enzyme where it was erroneously stated (based on superseded measurements) that the adding of a nucleotide to a nucleic acid chain was by itself not favored thermodynamically, when in fact it is slightly favored. The crucial importance of pyrophosphatase in keeping pyrophosphate concentration low in the cell remains, so the change is not very significant to the discussion. Modified the ends of the DNA sequence to conform to those in the OnScreen DNA Replication app. The simulation is unchanged.

App Description

Looks great on an iPad Mini as well as "full-sized" iPads. OnScreen Gene Transcription shows how DNA's genetic code actually works. Through the use of engaging 3D animations with a virtual double helix model it makes clear and memorable how a recipe for a protein stored in a gene is made available for use by being copied nucleotide by nucleotide in the construction of a messenger RNA molecule. Students from middle school on up can learn from the app, as no advanced knowledge of chemistry is assumed. The model is exactly the same as the one found in OnScreen DNA Model, a companion app that teaches the structural details of DNA. Detailed commentary on what the animations demonstrate is available in a popover view.

The sequence of events in gene transcription unfold in three-dimensional simulations that don't skip over the need for unwinding the DNA after the strands have been separated. The formation of a hybrid DNA-RNA double helix during RNA construction is correctly shown instead of the two-dimensional ladder structure sometimes depicted. Important details about transcription that are often given short shrift or omitted altogether, such as the essential role the enzyme pyrophosphatase plays in the cell, are included.

Set the simulation to pause after each new significant step or pause it only when you want. Commentary on what is happening is literally at your fingertip in a popover. Rotate, translate, or zoom the model during the simulated transcription for a better view just by finger slide gestures. Background material on DNA and RNA are found in the Useful Stuff popover.

The ball-and-stick model has the advantage of clarity at the expense of atomic detail. The RNA Polymerase enzyme complex, while not shown in the view with the DNA model, so as not to obscure what is happening with bonds and strands, is depicted in the Sequence View below the model, thus making the point that it moves along the DNA, as it initiates and controls the reactions in transcription. We know of no other simulation of gene transcription on the internet or anywhere else that shows what happens as thoroughly as OnScreen Gene Transcription does.

App Changes

Other Apps From OnScreen Science, Inc.