14 DAY TRIAL // From the color of your hair, eyes, and skin, face shape to all your skills and the way you laugh - everything's a combination of genetics, and how the activity of your genes was shaped by the environment.
You may have told your lover she has her father's big blue eyes and her mother's soft skin. Well, that's perfectly true: genes are inherited from the parents. Our bodies are made of about 100,000 billion cells. Inside the nucleus of each cell, there is the same DNA, compassing thousands of genes. Genes are DNA units controlling from our shapes and colors, to blood groups and any other traits. Thus, each cell contains the genes necessary for the forming, remaking and functioning of the body.
In the 4th century BC, Aristotle said the traits are transmitted through blood and that governed European thinking for two millennia, so that we talk about "blood connections" even today, when we want to say we are related to somebody.
During the 17th century, sperms and eggs were discovered, but their role was not understood. People believed that inside of them are minuscule creatures completely developed. But in the 18th century, scientists understood that an egg and a sperm must unite for forming an embryo.
In 1866, the Austrian monk Gregor Mendel, based on experiments made on pea, defined genes as "distinct heredity units" responsible for the transmission of the hereditary traits. In 1910 was found that genes are placed on structures located in the cell nucleus called chromosomes. Chromosomes are made of proteins and DNA (deoxyribonucleic acids). Till 1944, it was thought that the proteins, not the DNA, harbored the genes. In 1953, James Watson and Francis Crick discovered the chemical structure of the DNA, shaped as a spiraled chain molecule.
Look at the fullstop at the end of this phrase. About 500 medium sized cells fit in it. Some bacteria are 50 times smaller than this. As an egg's yolk is a cell, you could say the largest cell in the world, the size of a ping pong ball, is the ostrich egg yolk.
All animals and plants start from just one cell. From that initial cell, through division, 2 cells form, than 4, than 8 and so on. These first undifferentiated cells are called stem. They later start to differentiate in various types (muscle cells, nerve cells, skin cells and so on), forming tissues. Various tissues can form organs (like heart, lungs, and eyes). But each living cell contains a fluid mass called cytoplasm and in it, the nucleus wrapped in a thin membrane. The nucleus is the control center of the cell, as it coordinates all its activities. This is made through the genetic program encoded inside the DNA from the chromosomes.
DNA molecules are tightly curled packed inside the chromosomes. The DNA makes you an unique human being, and a dog different from a zebra, fish, rose or willow. The DNA amount of information comprised in just one cell could fill about one million articles to size of that you're reading right now.
DNA molecule is made from two twisted chains around each other, taking the shape of a twisted staircase. The two chains are joined by the combination of four types of bases. Each base is connected with its corresponding base on the other chain. The sole possible combinations are thymine-adenine, adenine-thymine, guanine-cytosine and cytosine-guanine (those, there are only 4 type of nucleotidic bases: adenine, thymine, guanine and cytosine). These pairs of bases form the stairs of the twisted DNA staircase.
The genetic information is established by the exact succession of the bases on the DNA molecule. This sequence establishes from your color hair to you nose shape.
Over 50 % of the molecules in most organisms are proteins. They form most active chemicals in the cells and are made of small building blocks called amino-acids (AA), about 20 varieties. Some can be produced by the body, others must be ingested.
Proteins have various roles: hemoglobin from the blood's red cells transports oxygen to the tissues, antibodies fight against germs, insulin metabolizes sugars and fats, myoglobin from the muscles produces muscular contraction, keratin form nails, hair and the external skin. There are thousands of proteins in the body, and hundreds in each cell. In fact, most of them act as enzymes, controlling the activities of non-protein substances.
In fact, this is what genes encode: proteins. These proteins can be structural (like keratin), functional (like enzymes or insulin) or controllers of the activity of other genes. Three pairs of bases form the sign of an AA from the protein. The sequence of bases on the DNA stretch forming a protein determines the amino-acids sequence in the encoded protein. But the information from DNA must be passed into cytoplasm to ribosomes, organelles which are involved in protein synthesis.
This is made with the help of a mono-chain molecule called RNA (ribonucleic acid, in which thymine is replaced by uracil). A special protein activates the gene (the DNA stretch), turning apart the two chains so free nucleotidic bases can join to form an RNA chain, imprinting the base pattern of a DNA chain.
The ribosomes read the information brought by this so-called RNA messenger and start the protein synthesis. For reading this information, the ribosomes use transfer RNA, carrying at one side a nucleotidic base, and at the other a corresponding amino-acid. The ribosome crosses the RNA messenger while starting to from the protein molecule chain. Most proteins have over 100 amino-acids. Shorter proteins are called amines. While forming, the protein starts folding itself into its functional molecule shape.
But during the cell division or production of reproductive cells, DNA must be duplicated with high fidelity. In fact, even from the beginning of the life, the current formula of the DNA was selected as heredity material because of its stability, decreasing to minimum the errors made during the protein synthesis or caused by mutations (changes in the base pattern of the DNA), guaranteeing the strict accomplishment of the hereditary laws.
DNA duplication is made this way: the two-chain molecule is split into separate chains by a special protein. Free bases start to form new chains with the newly freed DNA chains, following the rules of the bases match. Subsequently, two new double-chain DNA molecules result, both identical with the initial one.