What are Genes?
Through the Human Genome Project, it can be stated that humans have 20,000 to 25,000 genes. Now you might be wondering what are genes in the first place? Well, genes are structures located within every eukaryotic cell’s nucleus, tightly packed into chromosomes which each contain hundreds to thousands of genes each. Specific to humans, there are 46 chromosomes within each cell. These chromosomes when compared from cell to cell within the human body are completely identical. The reason for this congruency is because whenever a human offspring is created, 23 chromosomes come from the male and another 23 come from the female which conjoin to form a single cell containing 46 chromosomes.
This single cell multiplies and multiplies to create a baby which grows into an adult human composed of trillions of cells. Now due to the fact that all the cells in our body came from a single cell our genes are identical to that of the single cell giving reason to why the chromosomes throughout our cells are the same.
Now this ability for cells to divide in rapid amounts and still keep the genes given by their predecessor intact is due to the structure of the chromosome in which our genes are stored. Chromosomes are made of proteins known as histones and a single molecule of deoxyribonucleic acid. Inside the chromosome, the deoxyribonucleic acid is wrapped tightly around the histones allowing for 3 meter long DNA molecules to fit in the cell’s nucleus with ease. Additionally, the chromosome structure contains a constricted region which we call the centromere. The centromere is responsible for keeping the chromosomes aligned and also serves as an attachment site for the two replicated chromosomes during the complex process of cell division. Another component of chromosomes are the telomeres which are repetitive stretches of DNA located at the ends of linear chromosomes. These components prevent the DNA from getting damaged and unraveled. Everytime the cells within an organism divide, they lose a little bit of their telomere and when this part of the chromosome is lost completely, the cell has no other option but to die. However, telomeres in some cells like white blood cells are repaired by special enzymes known as telomerase which overall allows for white blood cells and other cells of the same kind to multiply way more.
As you can see in the structural diagram above, you may notice that everything boils down to what we call deoxyribonucleic acid (DNA). DNA is the blueprint of our body and it contains information that tells our body what to do. The significance of DNA is huge as without it no living thing would be able to survive. In terms of the building blocks of this magical material, it is nucleotides. A nucleotide is a compound consisting of a nucleoside linked to a phosphate group; this structure forms the basic structural unit of nucleic acids such as DNA. The nucleoside part of the nucleotide is a compound consisting of a purine or pyrimidine nitrogen base linked to a sugar molecule. The purines have a double ringed structure with a six membered ring fused to a five membered ring. While pyrimidines are smaller in size having a single six membered ring structure. In terms of the sugar component of the nucleoside, it is the sugar chemically known as deoxyribose. Below is an examples of one nucleotide which consists of the pyrimidine base thymine(T), the 5-carbon sugar: deoxyribose and a phosphate group:
Looking at this nucleotide, you might be confused how this forms the double helix DNA structure we see everywhere. Well when we take a look at DNA it has four nucleotides which are adenine(A), thymine(T), cytosine(C) and guanine(G). These four nucleotides when combined in accordance with complementary base pairing format where adenine can only link with thymine and cytosine can only pair with guanine, we get the DNA double helix structure. And when DNA is broken down into sections based on purpose, we get different genes. Overall genes are the blueprints for life and serve many purposes within an organism. One of the major purposes is the role they play in protein synthesis which is the basis of creation for anything in the human body.
