Critics on the origin of species were asking about transitional forms. If new species were continually evolving, then there ought to be lots of intermediate forms scattered across. That was their main concern.
Darwin couldn't properly give the satisfactory idea that time.
If your two parent hadn't bonded just when they did, possibly second to nanoseconds change and you wouldn't be here. Go beyond on generation to generations, you are result of so many genes along the way and most of the people you meet along your way up are your relatives on genetic level. With very few exception every cells almost 99.99% carries same component of chromosomes. (except RBC, Immune cells, eggs and sperms).
DNA exists for only one reason to create more DNA. Evidence suggested that DNA somehow involved in making proteins, yet it was clear that proteins were being made outside nucleus away from DNA. RNA acted as intermediate. Its like as if one spoke spanish and other Hindi, with RNA being translator with chemical clerk ribosome. RNA translates information from DNA into terms proteins can understand and act upon.
Scientists work:
Morgan tried his best to produce mutation in Drosophila melanogaster, finally discovered white eye color. Oswald, inoculated strain of bacteria and made it infectious by crossing with the alien DNA.
For the discovery of structure of DNA, Watson was mastering art of Crystallography, Crick completing a thesis on X-rays diffraction of large molecules. Franklin was unreasonable, secretive woman made best picture for possible DNA structure.
Genes are nothing more than instructions to make proteins. They are rather like keys of piano, each playing single monotonous note. But combine as you would combine piano keys and you can create chords and melodies of infinite variety. Put all genes together to form great symphony of existence called human genome.
Chromosomes are more like books and genes as individual pages of instruction for making proteins. Words on which instructions are written called codons and letters are bases. Most of the DNA replicates dutifully and absolutely, rarely a letter gets into wrong place causing single nucleotide polymorphism generally with no detectable consequences but sometimes slight advantage like more pigmentation, increased RBC production etc. But additional RBC also thickens blood, its like pumping oil into heart. For higher altitude, efficiency for breathing increases and heart problem risk also becomes higher. Hence we are all similar. Evolution won't let you become too different not without becoming a new species. Most of your DNA is devoted not to you but to itself. You are machine for the benefit of it, not it for you. Life as you will recall, just wants to be, DNA is what makes it so. DNA exists just to make themselves duplicative and double. Our body is devoted to them and serve to them, we are vessels for their whim, we produce protein that does nothing beneficial for us. It is startling that the largest portion of gene in any organism don't do anything at all, they just lie their and undergo selection during breeding season.
All organisms are slave to their genes, spiders/ salmons are prepared to die in the process of mating. To disperse one's gene is the biggest impulse in nature. Sex is really just a reward mechanism to encourage us to pass out genetic material.
Scientists put gene making mouse eye to the larva of fruit fly, the result- it not only made viable eye in fruit fly but it made fly's eye. Here, we have creature who hadn't shared common ancestors for 500 million years, yet could swap genes as if they were sisters.
It turned out that 60% of human gene similar with fruit fly and 90% with the mice.
Life it appeared was drawn up from single set of blueprint.
Hox genes instruct to make embryonic cells to develop into liver, neuron or blood cells.
Even our eye color is determined not by the single but by the complex gene working in alliance.
Proteome is much more complicated than genome. To function, protein not only must have necessary chemical component but must be folded in specific shape with the same looping, coiling, crinkling.
( Reference: The histroy of Almost everything By Bill Bryson)
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