The material of this article will familiarize the reader with basic concepts of genetics, and with interesting properties of the human genome. Genetics is the science of patterns of heredity and variability. Depending on the object of research, the genetics of plants, animals, microorganisms, humans and so on are classified.
So, all the great multitude of organisms that inhabit the Earth’s biosphere, bacteria, plants, animals and humans: all of these are carbon, oxygen and hydrogen, organized into complex cellular formulas that store, among other things, hereditary information about what a given living organism and its offspring should be.
Each organism is made what it is by a set of its genes. Genes are a collection of instructions given to the offspring by their parents. These “instructions” are hidden in every cell of every living organism and are stored on long strands of substances called DNA. DNA stands for deoxyribonucleic acid. And these long strands, compactly twisted into an “X” or “U” shape, are called chromosomes. Chromosomes are made up of many genes. A single gene is a particular sequence of DNA that contains cellular instructions.
The DNA is like a ladder and is called a “double helix. The steps of this ladder consist of four basic elements called bases: Adenine, Thymine, Cytosine, and Guanine. The specific sequence of the set of A. C. T. G. is of great importance. It is what determines whether a living organism is a banana, a rhinoceros, or a human. It determines whether a person will have brown hair, blue eyes or white skin. The length of this ladder is made up of alternating molecules of phosphate and sugar.
The entire genetic sequence as a whole is called the genome, and each person has three billion two hundred million base pairs in the genome. Someone would have to type at a hundred words per minute for eight hours a day to list all the components of the human genome within five years. And if you stretch the DNA strand of just one human cell, it would stretch to the full height of a human being. If you do the same with the DNA from all the cells, you can stretch a string from the Earth to the Moon six thousand times. The entire human genome would take up three terabytes of computer memory. And yet, in terms of the genome, humans are 99.9% alike. Our genetic constructs differ by only 0.1%.
At the same time, only 2% of human DNA gives intelligible instructions to the body, everything else is called “useless DNA”, because at the moment it is believed that it is not responsible for anything. It takes only eight hours for a single cell in the human body to fully copy its complete DNA sequence. Each person is exactly who he is because of his genes.
So, we have already realized that humans are 99.9% similar to each other in terms of our genome. But a science such as genomics (a branch of molecular genetics devoted to the study of the genome and genes of living organisms) can give us some more interesting figures and tell us how much the human genome coincides with the genome of other animals and plants, such as monkeys. So here is some data from the scientists:
The DNA of two humans who are identical twins is 100% identical;
Human and chimpanzee DNA are 98.7% identical;
human and gorilla DNA are 98.4% the same;
Human and mouse DNA are 98% the same;
Human and dog DNA are 95% the same;
Human and banana DNA are a 50% match;
human and daffodil DNA are 35% the same;
human DNA and caenorhabditis elegans (a round worm about 1 mm long that is widely used as a model organism in genetics research) have a 74% match.
These and other similar data from comparative genomics have given a very big boost to the development of medicine and biology. They made it possible to understand which animal species are close to each other and which are not. For example, it turned out that different species of whales are very similar to the hippo, in terms of their genomes, although visually they are not so similar. This suggests that the whale and the hippopotamus share distant ancestors.
But the most useful information about the similarities and differences between the human and other animal genomes was in medicine. After all, thanks to this information, it became clear on which animals it is best to “practice” drugs and methods for treating various diseases. And while chimpanzees and gorillas turned out to be not very successful and convenient test subjects, biologists and other scientists working on new drugs and treatments have not spared mice at all, but have put them through the most various experiments, first infecting them with various diseases and then trying to cure them.
So, now you know more about the microscopic structures that make us the same, but at the same time give each of us certain properties, make each person special.