coding

Chapter 2

When you are conceived in your mother's uterus you are an ovum that has been fertilized by a spermatozoon that rapidly starts dividing its cells called a Zygote. (Ovum is the singular technical term for an egg cell; the plural is ova. Spermatozoon is singular; spermatozoa is plural. The abbreviated term for these words is 'sperm' and it is casually used as both singular and plural. But it's not nearly as much fun to say. Try it! Sperm. SPERMATOZOON! Both cells are capable of active movement but the egg cell is significantly larger, about 30x bigger, and it is visible to the naked eye, unlike the sperm cell.)

The reason that anything at all happens when a sperm cell meets an egg cell is because they both contain chromosomal pairs. Humans have 46 chromosomes (expressed in pairs) that we get from our parents; 23 from mom and 23 from dad- 23 pairs, 46 chromosomes. Chromosomes are these spindly x- shaped structures that contain our DNA.

DNA stands for deoxyribonucleic acid and is one of the four major types of macromolecules that are essential for all known forms of life; it stores biological information. Most DNA molecules consist of two strands coiled around each other to form a double helix or thread-like chain of nucleotides carrying the genetic instructions used in the growth, development, functioning and reproduction of all known living organisms and many viruses.

More than 98% of human DNA is non- coding, which means they do not serve as patterns for protein sequences. Instead, this 98% of information is dedicated to making non- coding RNA some of which regulate gene expression. (If DNA is the blueprint, RNA is the construction worker). Other non-coding DNA is used to regulate the transcription and translation of protein-coding sequences, attach the chromosomes to the cell nucleus, start DNA replication, attach chromosomes into their famous x-shape during reproduction, and as 'end caps' so to speak that protect the rest of the DNA from deteriorating or attaching to another chromosome.

And lastly, there are a number of pseudogenes held within your DNA; these are genes that are copied but that have been 'turned off' due to mutations. Usually, these genes stay inactive and represent a sort of fossil record of the genotype, but sometimes they can be used as raw genetic material in the making of new genes through processes like gene duplication and divergence. (Genes are segments of DNA that hold information that determines your physical features.)

All of these things are interesting and no doubt of importance, but what I'm interested in is the other 2%- the part that codes for things like eye, hair, and skin colour, height, or your nose. All of the genes in your body are called your 'genotype' but the specific genes that code for what you look like are called your 'phenotype'. You get your phenotype from your parents just like your other genes except these phenotype genes come with a catch: they come in strong and weak varieties. They're referred to as either 'dominant' or 'recessive' and they function accordingly.

You can receive your phenotype genes from your parents in a variety of combinations. Generally speaking, among all types of colouring that are determined by genetics, dark colours are dominant and light colours are recessive. So, if both your eye colour genes are the same, your genes are 'homozygous' and if you have one dominant and one recessive gene, they are called 'heterozygous'. Your phenotype will express a dominant trait if it is homozygous (the only option) or heterozygous (dominant overtakes recessive) but you will only express a recessive trait if the genes are homozygous.

One important thing to remember is that genes do not code in a one to one manner. It's more of a team effort in that it's more like this gene effects this gene which effects this gene and altogether the end result is that you have brown hair.

Without your own personal and unique phenotype you wouldn't look like the 'you' that you and the people around you see when they picture 'you'. The way you look can affect you so much. You should always be confident in how you look; the beautiful complicated set of circumstances that had to coincide to result in your one of a kind look is awe inspiring! Don't worry about the typical 'beauty standard'. The only person that should concern themselves with how you look is yourself. Even if it's unconventional or unpopular, changing, adding, or taking things away, you should always love yourself.

--- --- --- --- ---

*FUN FACT: Mitochondrial DNA (mtDNA) was the first significant part of the human genome to be sequenced. (DNA sequencing is the process of determining the precise order of nucleotides within a DNA molecule.) In humans, the 16,569 base pairs of mitochondrial DNA encode for only 37 genes. In most species, including humans, mtDNA is inherited solely from the mother. Scientists aren't really sure why that is because both female eggs and male sperm have mitochondria. The two theories about why this happens are 1) the egg has a significantly larger number of mitochondria, something like 100,000 compared to the 50- 100 in a sperm cell, so that it is assumed the eggs mtDNA simply takes over because of sheer number, it's that or 2) the egg cell is somehow destroying the sperms mtDNA. Either way that it turns out, this coincidence has been extremely helpful in determining the origin of the first homo sapiens.