Gene Expression Stages

Fig. 1: Genes in the nucleus must control events throughout the cell. Image by P. Hain

Fig. 2: Transcription of DNA takes place in the nucleus. Image by P. Hain

Genes are located in the nucleus of plant and animal cells while proteins are made in the cytoplasm (Fig 1). How does the genetic information get transferred from the nucleus to the cytoplasm so the correct proteins are built in the right cells at the proper time? First the gene is turned on and the process called transcription takes place. (Fig. 2) Briefly, transcription means reading DNA and making an RNA molecule. Next the RNA leaves the nucleus and enters the cytoplasm so that it can be read to build the protein (Figs. 3,4,5).

Fig. 3: Translation of RNA takes place in the cytoplasm. Image by P. Hain

Fig. 4: Translation of RNA to build a protein. Image by P. Hain

Fig. 5: Proteins control cell events. Image by P. Hain

The process of reading RNA and making protein is called translation. Transcription allows copies of the needed genetic information to reach the site of protein synthesis. Translation allows the cell to read the genetic information to make proteins needed to drive development and maintain essential metabolism. Proteins can function as enzymes, structural molecules or regulatory molecules. The components of gene expression work the same way in all living cells. Prokaryotes will differ in some respects from eukaryotes because they lack a nucleus/cytoplasm compartmentation. As an example, we will focus on the expression of a gene found in both plants and bacteria called ALS but the processes can be applied to many other genes.*The following animations have no audio.*