--------- #1300 - Why Every Genome is Different?
- Every human genome is different otherwise we would all be identical, human clones exactly alike. What’s a genome? And, what is different that makes individuals out of 3,000,000,000 humans.
- Attachment - none
- The genome is the manual with instructions to build a human being.
- The chromosomes are the chapters in the manual.
- The genes are the individual instructions that make the proteins.
- All the words in the manual are from a 4 digit, AGCT code in the DNA.
- Most all the life on Earth shares this same chemistry, bugs, trees, and elephants
- Chromosomes are made of long strands of deoxyribonucleic acid, or DNA for short.
There is about 6 feet of DNA strands squeezed into every cell in your body. Each strand of DNA contains 3,200,000,000 letters of the AGCT code. That would amount to 5,000 books just to print out all those letters. If all the DNA strands in our body were tied end to end they would stretch back and forth from the Moon 26 times. The estimated amount of your DNA threads is 12,420,000 miles, the distance to the Moon is 238,855 miles.
- Chromosomes are composed of DNA and carry the genes that pass on the heredity. Chromosomes exist as a tangle of threads (chromatin). The proteins (histones) bind the DNA to organize the threads that we call chromosomes.
- Most bacteria have a single circular chromosome. Higher organisms , like us, have threads of chromosomes. Each species has a fixed number of chromosomes. For humans it is 46, 23 from your father and 23 from your mother, coming from the sperm and the egg, and coming together during fertilization.
--------------------- females have 2 “X” chromosomes.
--------------------- males have an “X” and a “Y” chromosomes.
- Every cell in your body contains a nucleus and every nucleus contains these 46 chromosomes. Almost every cell in our body contains exactly the same configuration of chromosomes. 99.999 % are identical. The cells that are exceptions are red blood cells, some immune system cells, and the egg and sperm cells.
- Genes are nothing more than instructions to make proteins.
- Add up all the genes and you have the human genome.
- The shape of the DNA molecule is a twisted rope ladder. The uprights of the ladder are a sugar, called deoxyribuse. The rungs of the ladder are the AGCT code components with “ G” and “C” always paired. And, “ C” and “T” are always paired. The four DNA components are:
----------------- A = adenine
----------------- G = guanine
----------------- C = cytosine
----------------- T = thymine
- Guanine is always paired with cytosine, GC
- Thymine is always paired with adenine , TA
- The order in which “ GC” and “AT” appear in the rings of the ladder is the human genome code. When the DNA wants to reproduce the ladder rings part down the middle, they unzip like a zipper on a jacket, with each half separating to form a new partnership. Each separated strand serves as a template for forming a new matching strand. As they pair together “G” always goes with “C” and “A” always connects with “T”. This all happens in the cell in a matter of seconds. A DNA replicate itself. That is the secret of life, but, the DNA itself is not alive.
- Most of the time the DNA replication is perfect.
- However, once in a million cases there is a chance occurrence that allows the letters to get in the wrong place. This mis-letter might make the person more susceptible to some disease. Or, it might predispose the person to some advantage, say red blood cells that are more adaptable to high elevations. The whole Darwinian theory is that the good adaptations survive and the bad adaptations die.
- If mutations make a person too different he becomes a new species. In order to stay the same species our DNA must be 99.9 % the same. But, on the other hand it is the 0.1% difference that makes all of us different individuals.
- From the evolutionary point of view sex is just a reward mechanism to encourage us to pass on our genetic material. The DNA in our genetic material simply wants to reproduce itself.
- As mentioned earlier we humans have 46 chromosomes. More complex organisms do not just have more chromosomes. In fact there are ferns that have 500 chromosomes. The common newt has more than 200 chromosomes. With our 46 chromosomes it is estimated that we have about 35,000 genes. In a very few cases a disease or some disorder is caused by a single dysfunctional gene. But, things are not that simple because in most disorders it is not a single gene but some mysterious alliance between many genes that create the disorder. Obviously, this is making medical research much more challenging.
- We understand the human genome as the “parts list” for the human body, but, that does not begin to tell us how it works. It has taken life over 3,800,000,000 years to work out this system we are using, so, it not surprising that it make take us a few years to figure it out. We are convinced it all started from a single source. Even people and bananas share the same chemical reactions to live. Somehow our chemical processes got more complicated, but they remain basically the same. And, people and bananas are able to pass on their secrets to the next generation. If you look at the common AGCT codes for each species there is not much difference in percentages:
--------------------------- ---------- “A” ---------- “ G” ------ “ C” -------- “T”
---------------- Human ----------- 30.4 ------------ 19.6 ------- 19.9 ----------- 30.1
---------------- Sea Urchin ------ 32.8 ------------ 17.7 ------- 17.3 ---------- 32.1
---------------- Wheat ------------ 28.1 ------------ 21.8 -------- 22.7 ----------- 27.4
---------------- E Coli Bacteria -- 24.7 ------------ 26.0---------- 25.7 ----------- 23.6
- In 1977 science first broke the ACGT code.
- The first genome sequenced was the 5,375 pairs in a bacterial virus. Viruses are parasites and not considered living organisms.
- In 1995 the first living bacteria was sequenced with 1,830,138 pairs ( 1,743 genes)
- In 1998 the first animal sequenced was the round worm
- In 2000 the first plant sequenced was the mustard.
- In 2001 the human genome was sequenced at 2,910,000,000 pairs with 35,000 genes.
That is what we pass on to our children. They should be 99.9% exactly like us, but, that 0.1 % makes them individuals. I can look at my 3 kids and say they are all alike, and, at the same time, they are all different. Nanotechnology will soon be taking us to the next level of atomic biology. An announcement will be made shortly, stay tuned. We have a lot to learn how all this stuff works.
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707-536-3272, Tuesday, September 13, 2011
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