Sunday, 25 June 2017

gene

                                                                   What is gene?


                       Gene are small portion of DNA within the genome that code for proteins.
                     they contain the the instruction for our individual characteristics-like eye
                     and hair colour.Genes can acquire mutations in their sequence, leading to
                     different variants, known as alleles, in the population. These alleles encode
                     slightly different versions of a protein, which cause different phenotypical
                     traits. Usage of the term "having a gene" (e.g., "good genes," "hair colour 
                     gene") typically refers to containing a different allele of the same, shared
                     gene. Genes evolve due to natural selection or survival of the fittest of the
                     alleles.
       


                          * A gene is a small section of DNA that contains the instructions for a 
                             specific molecule, usually a protein.

                          * The purpose of genes is to store information.

                          * Each gene contain the information required to build specific proteins
                             needed in an organism.

                          * The human genome contains 20,687 protein- coading genes.

                          * Genes come in different forms called alleles.

                          * In humans alleles of particular genes comes in pairs, one on each
                            chromosome ( we have 23 pairs of chromosomes ). If the alleles 
                            of a particular gene are the same, the organism is described as                                               homozygous for that gene. If they are different the organism is called
                            as heterozygous for that gene.

                          * An individual phenotype is determined by the combination of alleles
                            they have. 

                          * For example, for a gene that determines eye colour there may be 
                            several different alleles, one allele may result in blue eyes while
                            another might result in brown eyes. The final colour of the individual 
                            eye will depend on which alleles they have and how they interact. 

                          * The character associated with a certain allele can sometimes
                             dominanat or recessive.
                                                                    History
                  The existence of discrete inheritable units was first suggested by Gregor Mendel
                  (1822–1884). he studied inheritance patterns in 8000 common edible pea plants,                                  tracking distinct traits from parent to offspring. He described these mathematically as                              2n combinations where n is the number of differing characteristics in the original peas.                            Although he did not use the term gene, he explained his results in terms of discrete                                inherited units that give rise to observable physical characteristics. This description                                prefigured the distinction between genotype (the genetic material of an organism)                                  and phenotype (the visible traits of that organism). Mendel was also the first to                                        demonstrate independent assortment, the                                                                                                  distinction between dominant and recessive traits, the distinction between                                                a heterozygote and homozygote, and the phenomenon of discontinuous inheritance.  
                     Mendel's work went largely unnoticed after its first publication in 1866, but was                                        rediscovered in the late 19th century by Hugo de VriesCarl Correns, and 
                     Erich von Tschermak, who (claimed to have) reached similar conclusions in their own                            research. 
                                        
                                                             Gene expression  

                     In all organisms, two steps are required to read the information encoded in a gene's DNA                       and produce the protein it specifies. First, the gene's DNA is transcribed to messenger                          RNA (mRNA). Second, that mRNA is translated to protein. RNA-coding genes                                        must still go through the first step, but are not translated into protein. The process of                              producing a biologically functional molecule of either RNA or protein is called gene                                  expression, and the resulting molecule is called a gene product.   
   
                            


                             

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