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Sample Essay on What is Gene Expression

What is Gene Expression?

Gene expression is the synthesis of gene products using genetic instructions. These products are mainly proteins and end up performing essential functions like enzymes, receptors and hormones in the body. In cases where genes do not code for proteins like ribosomal RNA or t-RNA, code for functional RNA products. An important element in this process is the gene. Importantly, genes are subunits within the DNA, which is the information database of the cell that occurs in the nucleus of a cell.

The DNA has the genetic blueprint of the cell used to make proteins that meet the needs of the cell. Every gene has a unique set of instructions, which are used to code for a particular protein. The structure of the DNA shows two long paired strands that form a double helix. Each strand has building blocks known as nucleotide bases. The bases are adenine, thymine, cytosine, and guanine (A, T, C and G). They occur in triplets, which represent a particular amino acid.

Regulation of gene expression in human body

Genes express themselves as either RNA or protein. While this is the case, not the entire gene product is useful all the time. Similarly, body cells need genes in deferent quantities depending on the purpose they will serve. In fact, the amount of energy to for a cell to express all the genes all the time would be unbearable. Moreover, some gene products are toxic to the cell and only express themselves when a cell dies to prevent harm. These reasons explain why gene expression is an important process.

Cells have a complex system of mechanisms, which help to monitor their activities and the environment. These mechanisms play a crucial role in determining what gene the cell requires, the time and the appropriate quantities. Body cells receive internal and external signals, conduct an analysis and decide the type of gene product needed. Once the cells make this decision, they create a gene product. The first step in the making of a gene product is the production of a copy of the gene. This is necessary because genes cannot leave the cell nucleus. This new copy of the gene is called messenger RNA or simply mRNA. Unlike the original gene, mRNA can exit the nucleus. The initial step when making mRNA is the binding of the transcription factor on to the DNA at a region that is upstream to the target gene.

DNA Transcription

Transcription is a process that allows RNA synthesis and is regulated by the reaction between promoters and enhancers. During transcription, different types of RNA are produced, like mRNA, which is important in specifying the sequence of amino acids present in the protein product. Others are transfer RNA or tRNA and ribosomal RNA, rRNA, which is key during translation. During gene expression, transcription takes place in the following four steps:

Step 1: Initiation – This is where the DNA unwinds and detaches to form an open complex. This allows RNA polymerase to cleave to the promoter of the template strand.

Step 2: Elongation – During this second stage, the RNA polymerase moves on the template stand, producing an mRNA molecule.

Step 3: Termination – It occurs in two different ways in prokaryotes. For example, in Rho-dependent termination, Rho, a protein factor disrupts the complex, which involves the template strand, RNA molecule, and RNA polymerase. In Rho-independent termination, a loop develops at the terminal of the RNA molecule, causing it to detach

Step 4: Processing– this is the final stage, where the RNA molecule is processed in different ways. For instance, introns are removed with the splicing together of exons to form a fully developed mRNA that has a single protein coding sequence.

Gene expression in different cells

Gene expression takes different in various cells. Notably, a section of cells genes are expressed at any given moment. The differences in the manner in which different cells genes are expressed arise from the fact cells have unique sets of transcription regulators. While some of these regulators enhance transcription, others act as inhibitors, or suppressors, disrupting the entire process.

In some cases, regulatory proteins affect transcription of multiple genes. This happens since several copies of the protein binding sites occur within the genome of a cell. As a result, regulatory proteins can assume a range of roles for various genes.

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References:

http://www.nature.com/scitable/topicpage/gene-expression-14121669

http://www.ncbi.nlm.nih.gov/probe/docs/applexpression/

http://www.news-medical.net/health/What-is-Gene-Expression.aspx

http://www2.le.ac.uk/departments/genetics/vgec/schoolscolleges/topics/geneexpression-regulation

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