From DNA to Protein: The Central Dogma of Genetics.

We know where DNA is stored; we understand how cells divide, but how is DNA relevant to cell, tissue, and organ function? Well, remember how DNA sequences (genes) are a code or “recipe”? The sequence tells the cell what proteins to make. Let’s look at your hair follicles; at specific points, in time, the cell needs to produce more hair (keratin) right? So, the cells need to receive signals that tell it what proteins to make. Signals can differ between function, requirements, and location of the cells.

Proteins are made up of poly (many) peptide chains, these peptide chains are constructed on cellular components called ribosomes. Ribosomes are “little factories” inside cells that read the gene sequence and turn it into a chain of amino acids. However, how does the sequence get to the ribosome, since chromosomes never leave the nucleus? RNA! RNA is DNA’s cousin; it is made up similarly but has a couple cool differences that make it a versatile and useful addition. RNA has many functions in a cell, but here the key players are mRNA (messenger RNA) and tRNA (transfer RNA). A process called transcription makes a copy of the DNA sequence in the nucleus onto mRNA and substitutes thymine (T) with uracil (U). This mRNA molecule then leaves the nucleus and binds to a ribosome to begin translation. Translation is the conversion of gene sequences into protein polypeptide chains. The gene sequence is read in groups of three letters (called a codon) and the tRNA search for the amino acid that matches the codon. The amino acid is then brought to the ribosome to be assembled into the protein polypeptide chain in the correct order to make the right protein! Once the sequence is finished, the polypeptide chain is released and folded neatly. Variations in the original gene sequence can, therefore, cause variations in the protein product, and this is the foundation for variation between individuals! This process from transcription to translation is known as the central dogma, but not all organisms obey this rule. Viruses are really good at reversing this process and often do so in host cells!