Previously, we’d spoken about how DNA contains all the information needed for our body to produce essentially, us. But how do our cells transform this genetic code from just instructions, to the real thing? How did I end up with such frizzy hair? The answer is proteins, encoded by genes within our DNA. It is the function of proteins in our cells that make us who we are. The journey from DNA to protein is not simple, but we can simplify it into 2 main processes; Transcription and Translation.
Firstly, a protein enzyme known as RNA polymerase attaches itself to a strand of DNA and uses free nucleotides in the nucleus complementary to the nitrogenous bases in the DNA strand to make a strand of pre-messenger RNA (pre-mRNA). The pre-mRNA is an exact copy of the DNA (with the exception that Thymine is replaced by Uracil), and contains regions known as introns and exons. Exons contain the information needed to encode a gene whilst introns are just useless regions that goes into the bin. Splicing is the process responsible for taking out the introns and combining the exons in pre‑mRNA to make mRNA. The transcription of genetic information therefore refers to the production of mRNA from DNA, which includes the process of splicing.
Amino acids are the precursors of peptide chains, and the folding of peptide chains becomes protein. The process responsible for making peptide chains using mRNA is known as Translation and involves another type of RNA called transfer RNA (tRNA). Each tRNA has an amino acid attached to one end, and 3 nitrogenous bases attached to the other. The bases on the tRNA complementary to the 3 bases on the mRNA (known as a codon), will temporarily attach. For example, the codon Adenine-Uracil-Guanine (AUG) on the mRNA codes for the amino acid Methionine. As more tRNA attaches to the mRNA strand, amino acids on the end of adjacent tRNAs are brought close together and subsequently forms a peptide chain using multiple peptide bonds.
…And there you have it. Part 1 and 2 combined should have answered the question, “Why am I me?”. An explanation of how our DNA makes us, us! All of this is happening inside our bodies right now, without us even realising. Of course, I’ve probably missed out loads of details, but the point of my science posts is not to get you up to scratch for any exams but to enlighten some of you, maybe without a science background, on how amazing science truly is.