Gene expression

The title of the Project: Gene expression 

This virtual laboratory is intended for use in 11th grade classes on the following topics:

  • “Transcription. Post-transcriptional modification of pre-m ribonucleic acid. Stages of the Translation.”

Purpose of the virtual laboratory work:

  • To study the main stages of gene expression: transcription and translation.
  • To explore the key molecules: DNA, RNA, ribosomes, enzymes.
  • To investigate the influence of positive and negative factors on the transcription process

Virtual experiment

This virtual simulation of PhET allows you to visualize the complex process of gene expression at the cellular level in a simplified form.

1.Run the simulation. You will be given a choice of three different modes: Expression, mRNA, Multiple cells. Select the Expression mode.

2.On the screen you can see a long double-spiral DNA sequence and one particle isolated in its center-a gene. The gene consists of two different regions: regulatory and transcribed. The regulatory region is the place where transcription factors bind, and the transcribed region is the main DNA reading region that binds to RNA polymerase.

3.Now familiarize yourself with the symbols (take a look at the terminology below).

4. Gene expression consists of two main stages: transcription and translation. Transcription is the process of synthesizing an RNA molecule from a DNA molecule by RNA polymerase, resulting in the formation of an informational RNA(mRNA). Translation is the process of protein synthesis involving a ribosome from an mRNA  molecule.

Table 1.

5. Start experimenting. Drag the positive transcription factor from the toolbox to the regulatory region of “gene 1” by pressing and holding the left mouse button.

6.To start the transcription process, place the enzyme RNA polymerase at the beginning of the transcribed region. RNA polymerase immediately begins to synthesize mRNA, a complementary strand of DNA. This manipulation can be repeated indefinitely.

7.To stop transcription, replace the activating factor with a negative transcription factor. You will notice that the transcription process will stop because the repressor blocks the RNA polymerase, preventing it from binding with the transcribed region.

8.To start the translation process, install the ribosome complex at the end of the formed mRNA chain. You will notice how the ribosome will begin to synthesize a protein molecule, moving along the mRNA.

9.Add the resulting protein to the collection. Note that an unlimited number of proteins can be obtained from a single mRNA chain.

10.To stop the formation of proteins, bind the mRNA destroyer enzyme to the mRNA sequence. You will notice how the enzyme splits it into smaller fragments. This completes the expression of the 1st gene.

11.Click the “Next gene” button to start expressing the next gene. You may notice that it is longer than the previous one. Accordingly, the mRNA chain formed from it will be longer. Note that this gene requires two factors to activate transcription.

12.Perform the expression of the last gene by following the instructions provided above.

Conclusion

The virtual laboratory for gene expression provides a unique opportunity to visually study the complex processes of gene expression, as well as to investigate the influence of various factors on it.

Terminology

Gene – Ген – Ген

Protein – Белок – Ақуыз

Positive transcription factor – Активный фактор транскрипции(Индукторы) – Транскрипцияның белсендірілген факторы(Индукторлар)

Negative transcription factor – Негативный фактор транскрипции(Репрессоры) – Транскрипцияның өшірілген факторы (Репрессорлар)

RNA-polymerase – РНК-полимераза – РНҚ-полимераза

Ribosome – Рибосома – Рибосома

mRNA destroyer – расщеплитель мРНК – аРНҚ ыдыратқыш

Regulatory region – Регуляторный участок – Реттелуші аймақ

Transcribed region – Транскрибируемый участок – Транскрипциялық аймақ