How is a polypeptide chain related to DNA?

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dcbiostat eNotes educator| Certified Educator
DNA holds the instructions for the type and order of amino acids within a polypeptide.
Transcription and translation are the two phases of protein synthesis.
During transcription, the two strands of DNA unwind. One of the strands serves as a template for make an mRNA strand. Each set of three nucleotides on an mRNA is called a codon. These codons will be important in the second phase of protein synthesis called translation.
After the mRNA that is created during transcription, it migrates to the cytoplasm via a nuclear pore of the nucleus.   
During translation, mRNA, ribosomes, rRNA, tRAN, and amino acids work together to make the protein strand.
Once in the cytoplasm, the mRNA and ribosomes attach. The ribosomes serve as scaffolds that match the codons on mRNA’s to the anticodons on the tRNA’s. Anticodons are sets of three nucleotides on the base of a tRNA that are complementary to mRNA codons. On the top of tRNA are amino acids.
As the ribosome moves down the mRNA during translation, additional tRNA anticodons are matched with their complementary mRNA codons. In this way, amino acids that form a protein are arranged in the correct order.  When two amino acids are adjacent to one another, a peptide bond forms. The polypeptide chain continues to grow until a stop codon is reached on the mRNA strand.

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