Does an organism’s DNA code for proteins? The DNA code contains instructions needed to make the proteins and molecules essential for our growth, development and health. Only about 1% of the three billion letters directly codes for proteins. Of the rest, about 25% make up genes and their regulatory elements.
Deoxyribonucleic acid is the hereditary material in humans that contains the genetic code of organisms. It is responsible for bringing out the genetic variation in human beings.
It is a double helical structure formed by two polynucleotide chains that are complementary and run anti-parallel to each other.
Nucleotide Chains
These two nucleotide chains are the polymers of nucleotides. A nucleotide is a structural unit of DNA that is made up of- a sugar molecule (deoxyribose), a phosphate group, and nitrogenous bases.
Adenine and guanine are the two purine nitrogenous bases, and cytosine and thymine are the two pyrimidine nitrogenous bases found in the DNA. These nitrogenous bases determine the DNA sequence of our body.
Genes are a sequence of nucleotides that code for proteins or mRNA. DNA codes for proteins through the process of transcription and translation. The proteins are the molecules that help in the growth, development, and proper functioning of our body.
3 Steps By Which DNA Codes for Protein
Answer to the question, does an organism’s DNA code for protein? Yes!
DNA codes for proteins through an intermediate messenger called mRNA by the process of transcription.
The coding of DNA directly into proteins would lead to the loss of genetic material due to the insufficient coding amino acids. The template or the sense strand of the DNA is transcripted into an RNA sequence.
This occurs in three steps- Initiation, elongation, and termination.
- Initiation
The DNA sequence has a promoter region consisting of recognition sites for the binding of RNA polymerase. The binding of RNA polymerase results in the separation of the double-stranded DNA. As a result, a template of ssDNA is obtained for transcription.
- Elongation
The RNA polymerase reads the bases one by one on the template strand and creates a complementary RNA sequence of nucleotides. This RNA sequence completely resembles the non-template strand of DNA, except at the thymine position. RNA has the nitrogenous base uracil in the place of thymine.
- Termination
The terminator molecules terminate the process of RNA transcription by sending signals and releasing the transcript from the RNA polymerase.
Read Also: How Cell Uses DNA and RNA to Direct Protein Synthesis
Translation Process
The mRNA molecule is further translated to code for amino acids that build up to form protein molecules. The translation occurs in the cytoplasm of the cell, where the information present on the mRNA molecules is decoded with the help of genetic code.
Genetic code is a triplet of nucleotides, also called codons, that code for a specific amino acid. tRNA, also called transfer RNA, helps in the translation process by transferring the specific amino acid to the matching mRNA codon sequence.
The second step of gene expression, occurs in three steps- Initiation, elongation, and termination.
Initiation
An initiation complex is formed by the initiator tRNA and a ribosome that binds to the 5’ end of the mRNA. The initiator tRNA carries the amino acid Methionine, which binds to the start codon on mRNA sequence, hence starting the translation process.
Elongation
The ribosome moves to the other codon molecule, which is bound by the specific amino acid brought by the tRNA molecule. This step leads to the elongation of the amino acid chain.
Termination
The translation process is stopped when the ribosome binds to the stop codon sequence on the mRNA chain. The stop codons do not code for any amino acids and thus leads to the release of the polypeptide chain from the mRNA sequence.
This polypeptide chain or the amino acid chain is folded in various structures to form proteins in the endoplasmic reticulum. The gene expression in prokaryotes and eukaryotes differ a bit. The process is a bit more complex in eukaryotes.
Central dogma is the flow of genetic information in biological organisms. It is the process where the genetic information is carried from DNA to RNA molecules. These RNA molecules are further read to form protein molecules.
The flow of information from DNA to RNA is a reversible process, where the reverse step is called reverse transcription. The translation is the flow of information from RNA molecules to proteins and is a non-reversible step.
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