The Beginning of mRNA Is Not Translated
Interestingly, not all regions of an mRNA molecule correspond to particular amino acids. In particular, there is an area near the 5' end of the molecule that is known as the untranslated region (UTR) or leader sequence. This portion of mRNA is located between the first nucleotide that is transcribed and the start codon (AUG) of the coding region, and it does not affect the sequence of amino acids in a protein (Figure 3).
So, what is the purpose of the UTR? It turns out that the leader sequence is important because it contains a ribosome-binding site. In bacteria, this site is known as the Shine-Dalgarno box (AGGAGG), after scientists John Shine and Lynn Dalgarno, who first characterized it. A similar site in vertebrates was characterized by Marilyn Kozak and is thus known as the Kozak box. In bacterial mRNA, the 5' UTR is normally short; in human mRNA, the median length of the 5' UTR is about 170 nucleotides. If the leader is long, it may contain regulatory sequences, including binding sites for proteins, that can affect the stability of the mRNA or the efficiency of its translation.
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Advances in DNA technology have allowed for treatments such as gene therapy in the medical field. Nowadays, there are tools like the CRIPSR-Cas9 - harnessed from bacteria's immune system- that can nip a ‘bad’ region of DNA, which is responsible for disease, and replace it with a proper functioning bit. This is how genetic disorders are going to be addressed in the near future in mainstream medical facilities.
Recombinant DNA technology is being used to create clones of transgenic organisms that produce products of significance in the medical fields. An example is incorporating the insulin gene in bacteria genome. These clones of modified bacteria colonies secrete insulin protein that is purified and injected in diabetic persons to lower their sugar level to normal.
<span>The two tiles are not similar because segment PQ is to segment QR is 7 : 4 and segment JK is to segment KL is 4 : 3.</span>