Are all of your genes expressed in every cell in your body? Explain your answer and include an example in your explanation.
Ans. We have trillions of cells in our bodies. A variety of different organelles, such as decomposition of waste or production of energy, are present in each cell and play an important role in cell function. The largest organelle in the cell nucleus and here we find that our DNA (deoxyribonucleic acid) is tightly packed into structures known as chromosomes. Chromosomes are long-thread structures composed of DNA and protein molecules. Chromosomes bind closely during cell division into X forms and under a microscope are more readily visible. There are 23 chromosome-pairs in human cells.
Each chromosome consists of a DNA molecule consisting of a series of nucleotides arranged in 2 strands that resemble a double helix ladder. A base, a sugar, and a phosphate are composed of nucleotides. The four bases – adenine (A), guanine (G ), cytosine (C), and thymine ( T)-are combined (A with T and G with C). The order or sequence of these base pairs gives the knowledge essential to our organisms' growth and development. It may help to imagine the bases as letters in a certain order in the alphabet which shape words. These 'words' apply to the genes and function as a set of cell instructions for the functioning of cells.
Gene expression
We know that humans have around 25,000 genes since the human genome has been sequenced. Each gene provides a specific protein instruction or several protein versions at times. We are suggesting that the gene is expressed when a gene produces proteins in a cell. The expression of genes has two major phases. First, special cell structures read the gene and use the information to generate a molecular message in the form of a molecule of mRNA (messenger ribonucleic acid). The mRNA molecule then travels to the cytoplasm of the cell from the nucleus. A ribosome reads the message and produces a protein that corresponds exactly to the instructions of the gene and the process is called translation.
The same DNA and therefore the same genes are present in each cell of the body (other than gametes). In each cell, however, not all genes are expressed. We state that this gene is 'on' when a specific gene is expressed. When a gene is active, it creates proteins that influence the way the organism works or grows. To work properly, a cell must synthesize the required proteins at the right time. The protein's synthesis information encoded in their DNA controls or regulates all cells. Gene expression is called the process of turning a gene to create RNA and protein. Each cell regulates when and how its genes express themselves, whether in a simple single or complex multi-cellular organism. To do this, a mechanism needs to be developed to check the amount of protein that is produced by a gene to produce RNA and protein and when it is time to stop producing this protein because it is no longer required.
Gene expression control preserves energy and space. For an organism to express every gene at any time, it would take a tremendous amount of energy, so that it is more effective to use the genes only when necessary. Moreover, expressing only a subset of genes in every single cell saves space, because it is required, in order to transcribe and translate DNA, to unwound DNA from its closely coiled structure. If every protein was expressed continuously in every cell, cells should be massive. Gene expression regulation is highly complex. Dysfunctions in this process are harmful to cells and can cause many diseases, including cancer to grow.
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