[2013-2014]اقوى مذكرة مراجعة Biology للصف الثاني الثانوي الازهرى الفصل الدراسى الثانى
How are proteins made? Protein synthesis occurs by the processes of transcription and translation. In transcription, the genetic code contained within DNA is transcribed into an RNA version of the code known as messenger RNA (mRNA). The messenger RNA molecule is then translated to produce proteins.While transcription takes place within the nucleus of our cells, actual protein production through translation occurs in the cytoplasm. After leaving the nucleus, mRNA undergoes several modifications before being translated. Cell structures known as ribosomes along with another RNA molecule called transfer RNA (tRNA) work together to translate mRNA. A growing amino acid chain, also called a polypeptide chain, is produced in the process. The newly formed polypeptide chain undergoes several modifications before it becomes a fully functioning protein. Many copies of a protein can be made from one mRNA molecule because several ribosomes can translate the same mRNA molecule at the same time. To learn more about protein synthesis and the process of translation, see Protein Synthesis - Translation.
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