After some posts about the DNA, I would like to move on and talk about how the genetic information contained in the nucleus is actually translated into “concrete things” that will eventually generate living beings as we know them. Unfortunately, during the Biology course I did in high school we just received a small sneak peek on proteins, the “concrete things” produced with the information contained in the DNA. However, as my Biology teacher used to do for every new chapter, she tried to be sweet and short but still, she tried to condensate all the important facts.
Therefore, when she started talking about proteins, she raised the question of how the DNA, engulfed and protected inside a nucleus, could actually direct and give instructions to other players outside its environment, in order to produce proteins, the building blocks of every living beings. Having looked at our astonished faces (obviously, none of us ever thought about such a problem), she continued and talked about how nature, in its astonishing perfection, evolved a carrier able to transfer the instructions contained in the DNA outside the nucleus. These pieces of information are carried out in what is called cytoplasm, where they are then read and carefully followed to allow the production of proteins, used both inside and outside the single cells, maybe from neighbouring cells or tissues, but also circulating proteins, as it might be the case for the coagulation factors proteins that help us not to bleed out when we cut ourselves.
As I mentioned earlier, proteins are the building blocks of living beings and to give you a tangible example of a protein, its variability in between individuals and its functions, today for the SRF I will talk about head hair.
“Science Related Fact” (SRF):
A strand of hair has two basic components: the shaft, that is the black part that appears above the scalp, and the hair follicle, that resides in the skin and is not visible. Basically, we can think of the follicle as the organ responsible for producing hair. Evolutionarily, head hair was a big advantage for pre-humans, as it was protecting the scalp as they walked upright in the intense equatorial UV light. However, during the transition from Homo erectus to Homo sapiens, hair started to gradually change from straight hair (as it is the case for most mammals, including humans’ closest cousins, chimpanzees) to ‘kinky’ or curly hair. The rationale behind this theory is that curly hair better prevents the passage of UV light into the body relative to straight hair. However, by inverse logic, as humans moved farther from the equator, straight hair might have “evolved back” to help the passage of UV light into the body during the transition from dark, UV-protected skin to paler skin.
Nonetheless, as we might be able to guess now, curly or straight hair depends on the genes we inherited from our parents: curly hair is an autosomal dominant trait, which means, if one of your parents has curly hair, this dominant curly hair gene overtakes the straight hair gene and expresses itself in the offspring (see picture below).
Also, the composition of the hair strand impacts its texture. A study conducted in 2007 compared curly and straight hair fibers using electron microscopy: it was observed that curly hair have an uneven distribution of a specific kind of keratin (a protein and a primary component of hair), whereas straight hair were symmetrical in structure.