DNA to protein translation process - This one-way flow of information from DNA to protein is called the central dogma of molecular biology. Information stored in DNA is copied to RNA (transcription), which is used to assemble proteins (translation).
Each DNA strand is composed of sub-units called nucleotides or, “bases” for short. There are four types of nucleotides – adenine, A; thymine, T; guanine, G and cytosine, C. An A always pairs with T, and G with C. Thus the two strands of DNA are complementary to each other.
Nucleotides are arranged in a specific order on DNA – this is called the sequence of DNA. This sequence is further sectioned into genes – a short segment of DNA that is made into one polypeptide (protein) chain.
Cells convert DNA to protein in a two-step process.
Each DNA strand is composed of sub-units called nucleotides or, “bases” for short. There are four types of nucleotides – adenine, A; thymine, T; guanine, G and cytosine, C. An A always pairs with T, and G with C. Thus the two strands of DNA are complementary to each other.
Nucleotides are arranged in a specific order on DNA – this is called the sequence of DNA. This sequence is further sectioned into genes – a short segment of DNA that is made into one polypeptide (protein) chain.
Cells convert DNA to protein in a two-step process.
Transcription: DNA to RNA
Transcription occurs in the nucleus. Transcription in the process by which RNA is assembled from a DNA template. To transcribe a gene, the DNA is first unwound using the enzyme DNA helicase, which breaks the bonds between the nucleotide pairs. Then an enzyme called DNA polymerase “reads” one of the DNA strands and converts it into a complementary strand called pre-mRNA. Pre-mRNA is also made up of nucleotides, but uses uracil, U instead of T. Thus an A base on the DNA strand will result in a U base in the complementary mRNA strand.
After DNA is transcribed into a messenger RNA (mRNA) molecule during transcription, the mRNA must be translated to produce a protein. In translation, mRNA along with transfer RNA (tRNA) and ribosomes work together to produce proteins.
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Protein Synthesis: Transfer RNA
Transfer RNA plays a huge role in protein synthesis and translation. Its job is to translate the message within the nucleotide sequence of mRNA to a specific amino acid sequence. These sequences are joined together to form a protein. Transfer RNA is shaped like a clover leaf with three loops. It contains an amino acid attachment site on one end and a special section in the middle loop called the anticodon site. The anticodon recognizes a specific area on a mRNA called a codon.
The last set of codons (last three bases) of an mRNA molecule are called the “stop” codon – they do not have a corresponding tRNA. When the ribosome reaches this sequence, it detaches from the mRNA. The polypeptide chain (100′s to 1000′s of amino acids long) is released, and migrates to the Golgi appartus where it is modified (if required) and then eventually folds into a 3-D shape called a protein.
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