The dissection of this mechanism and its subsequent experimental imitation has been a boon to those interested in manipulating gene function. Ultimately, results from these kinds of studies have fundamental relevance, from the basic understanding of normal cell function, such as cell differentiation, growth, and division, to informing radically new approaches for treating disease. In fact, some human diseases can arise simply from a defect in a protein's three-dimensional structure.
Through the study of gene expression and proteins, it is easy to see how minute changes at the molecular level have a reverberating impact. Ribosomes, Transcription, and Translation. Gene Expression. Protein Structure. Protein Function. Aging and Cell Division. Calreticulin: a Multifaceted Protein. Enzyme Catalysis: The Serine Proteases.
It consists of two major steps: transcription and translation. Together, transcription and translation are known as gene expression. Translation, the second step in getting from a gene to a protein, takes place in the cytoplasm. Genes are composed of DNA and are linearly arranged on chromosomes. Some genes encode structural and regulatory RNAs. There is increasing evidence from research that profiles the transcriptome of cells the complete set all RNA transcripts present in a cell that these may be the largest classes of RNAs produced by eukaryotic cells, far outnumbering the protein-encoding messenger RNAs mRNAs , but the 20, protein-encoding genes typically found in animal cells, and the 30,o00 protein-encoding genes typically found in plant cells, nonetheless have huge impacts on cellular functioning.
Protein-encoding genes specify the sequences of amino acids, which are the building blocks of proteins. In turn, proteins are responsible for orchestrating nearly every function of the cell. Both protein-encoding genes and the proteins that are their gene products are absolutely essential to life as we know it. Genes Encode Proteins : Genes, which are carried on a chromosomes, are linearly-organized instructions for making the RNA and protein molecules that are necessary for all of processes of life.
The b interleukin-2 protein and c alpha-2u-globulin protein are just two examples of the array of different molecular structures that are encoded by genes. Replication, Transcription, and Translation are the three main processes used by all cells to maintain their genetic information and to convert the genetic information encoded in DNA into gene products, which are either RNAs or proteins, depending on the gene.
In eukaryotic cells, or those cells that have a nucleus, replication and transcription take place within the nucleus while translation takes place outside of the nucleus in cytoplasm. In prokaryotic cells, or those cells that do not have a nucleus, all three processes occur in the cytoplasm.
Replication is the basis for biological inheritance. Translation makes protein from mRNA. The ribosome generates a polypeptide chain of amino acids using mRNA as a template. Much of what is discussed above was originally discovered in bacteria, and then found to be true of archaea and eukaryotes as well; many of the core features of molecular biology are evolutionarily conserved.
However, there are a few key differences as outlined below. In prokaryotic cells, ribosomes begin to translate even while the mRNA is still being transcribed. This coupled transcription and translation can occur because prokaryotes have no nucleus.
In eukaryotes, the nucleus separates the transcription machinery from the translation machinery. In eukaryotes transcription occurs in the nucleus, whereas translation occurs outside the nucleus, in the cytoplasm by free cytoplasmic ribosomes or by ribosomes docked to the ER. Pre-mRNA has to undergo at least two, and usually 3, processing steps before they can be exported to the cytoplasm as mature mRNA. These are, in order:. All of these processing steps actually happen while the mRNA is being transcribed; that is, they occur co-transcriptionally.
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