Genetic Twist of Fate

I enjoyed “Genetic Twists of Fate” by Stanley Fields and Mark Johnston. They increased my non-scientific understanding of DNA, Genes and inheritance through clear writing and wonderful real-life examples to springboard to their understanding of mutations and diseases being passed down from generation to generation. A mutation that causes a disease, I gather, happens at a rate of 100%. The chance that mutation takes place in the joining of sperm and egg is only a possibility. Their chapter, “All from a Single Cell: How a Fertilized Egg Develops into a Baby” was illuminating. Each new cell carries an exact copy of the DNA and carries with it a set of switches that determine what part of the DNA will be acted upon to create the new cell type in the proper order. Wow! They try and tackle behaviors, but in my opinion don’t make their case. A mutation that causes a disease is 100%. A mutation, or genetic makeup that causes high IQ or any other behavior is never 100%. After looking at a complexity of DNA that cannot even be totally understood with all of the technology we have available to us today they boldly and condescendingly make their watertight case for evolution saying that the same DNA that we cannot even begin to understand totally now due to its complexity was present in the first single cell animal some 3.5 billion years ago because all of life uses the same genetic code with the same four nucleotides. Otherwise known as “the big accident” (my quotation marks, not theirs). From there it was one mutation after another that turned that first single cell organism into you and me. This after reading a book where every mutation mentioned caused disease and death; not selection and survival.

So other than the slap at my godly sensibilities; I enjoyed and recommend the book to read. One last point, I was reading simultaneously “Christian Persecutions in the Middle East” by George Marlin. He goes to great lengths to give us the history of the different Christian groups in the Middle East and the doctrines that separated them from Western Christianity. That separation centers around the nature of Jesus. The two books together gave rise to wondering about the possibilities of the DNA from Mary (even though it talks of the “seed of the woman”) and a perfect DNA from God being joined together in Jesus. For a Christian we look forward to a moment “when mortality puts on immortality”. Could that moment be tied to the DNA that comes from God, since we were created in His image? If I have crossed any theological boundaries, my apologies, just thinking out loud.

Here are some quotes:

“The consequences of altered genes can be seen all around us. Progress in unraveling the genetic basis of disease and behavior is also evident all around us. Hardly a day goes by without a story in a newspaper or on a website proclaiming that some gene has been found to contribute to the risk for a serious disease such as diabetes, cancer, or colitis, or a condition such as depression, alcoholism or autism, or a trait such as fearlessness, aggressiveness, or anxiety.”

Genetic fate – one miniscule change – “the difference between health and disease, between happiness and heartbreak, between life and death.”

“The more closely related two individuals are to each other, the more similar are their personal DNA codes.”

Our DNA codes are “99.9 percent identical…that 0.1 percent difference also results in some of us getting cancer, or Alzheimer’s disease, or having the good fortune to escape these diseases altogether.”

“They will be able to Google that code and predict their child’s risk for some diseases and behaviors. They will know what to watch for, and in some cases they will be able to intervene to minimize unwanted consequences and maximize desirable outcomes.”

“What is a gene? It is a stretch of DNA that contains the instructions for the cell to manufacture a protein.”

“There are compartments in the cell where specific functions are carried out, including maintaining the cell’s DNA, burning fuel to provide energy, and transporting material to where it needs to be.”

“Each room in a hotel has plumbing that connects it to a central water supply, a source of electricity to power its appliances, and heating and cooling units to control its temperature. A central processing system housed on the top floor of the hotel—a phone switchboard and a computer with an Internet connection—allows every room to be in contact with the front desk, and with all the other rooms in the hotel—indeed, with the rest of the world. Likewise, each cell connects to and communicates with adjacent cells and with the rest of the body using chemical and electrical signals.”

“In 1944, Oswald T. Avery…reported that they could dramatically change the properties of a cell—in their case a cell of the bacterium that causes pneumonia—by changing its DNA. They concluded that DNA was the long-sought substance of heredity.”

“How could such a “stupid molecule” determine what kind of covering enclosed a bacterial cell much less perform the amazing feat in more complex creatures of specifying the appearance of limbs and lungs and livers in all the right places and of the right size, and the proper number of teeth and toes, and irises and corneas and retinas that form eyes, and much, much more?”

“DNA is indeed a simple molecule. It is composed of only five atoms: carbon, hydrogen, oxygen, phosphorus, and nitrogen—the organic elements for which all living things are built.”

“When a cell divides to form two cells, it copies the two strands by peeling them apart—unplugging the plugs from their sockets—and then uses each strand as a template on which a new strand is synthesized.”

“the DNA from one human would reach to the sun and back more than sixty times.”

“If Isaac Asimov had had a mutation in both copies of his CCR5 gene—a mutation that resulted in the removal of thirty-two base-pairs of DNA—her would not have contracted AIDS. The HIV virus uses the CCR5 protein as a landing pad alighting on it before invading the cell. If Asimov had lacked those 32 base-pairs in his CCR5 gene his immune cells would not have had the HIV landing pad, causing them to be resistant to the virus.”

“People with MMA can only; partially break down the nutrients in mild and other foods…the problem was due to a missing protein that goes by the name cobalamin adenosyltransferase.”

“Proteins are the tiny machines that carry out nearly every cellular process, working in conjunction with other constituents of the cell to keep it alive and carry out its functions. The proteins in these machines are like gears and flywheels and valves: they fit together with exquisite precision and act in synchrony to carry out a specific cellular task.”

“When disease strikes, the immediate cause is usually the absence of a normal human protein…Cancer results from the uncontrolled division of cells, which can occur either because a protein that normally puts the brakes on cell division is defective, or because a protein whose job is to promote cell division is hyperactive.”

“Disease can also be caused by the presence of a toxic foreign protein. Cholera, diphtheria, botulism, and anthrax are caused by poisonous proteins that are released from bacteria that have invaded the body.”

“How is it that the sequence of amino acids in insulin instructs cells to take up the sugar glucose from the bloodstream, whereas a different sequence of amino acids of hemoglobin causes it to ferry oxygen around the body? Both proteins are composed of the same twenty amino acids; it’s the different order in which the amino acids are strung together that determines each protein’s distinct properties.”

“…has the DNA as the wiring diagram for the circuitry of the cell, RNA as the carbon copy of the diagram that gets carried to the fabricators, the genetic code as the legend that reveals what all the squiggly symbols in the wiring diagram mean, and proteins as the switches, batteries, lights, fuses, and other components of the circuits. A mistake in a part of the wiring diagram (a gene) can lead to a defective component (a protein), which can lead to a faulty circuit (diseased).”

“…proving beyond a reasonable doubt that virtually every one of our cells carries the same complete set of genes.”

“Most genes contain recognition sequences for several transcription factors. The sum of the effect of each transcription factor bound to the gene determines the state of the gene’s switch. Some transcription factors act to turn transcription on, others strive to turn it off. The transcription factors are like the transistors that constitute the motherboard of a computer, integrating the input they receive and responding with the coordinated output you see on your screen. This integrated circuitry of transcription factors bound near a gene constitutes the switch that turns the gene on or off.   Actually, these switches are more like rheostats that can be turned up or down, the brightness or dimness of the rheostat’s setting being determined by the particular combination of transcription factors that are bound to the gene. Since the human genome encodes about fifteen hundred different transcription factors, the number of different combinations of them is huge, so the rheostats can be set to an almost limitless number of levels. And since the settings of the rheostats on all 20,000 genes determine the identity of a cell, the great diversity of cell types in the human body should no longer be a surprise.”

“The whole developmental program, from the first division of the fertilized egg to the birth of a fully formed organism consisting of trillions of cells, is largely a diversification of the transcription factor collections in cells as they divide. How does a cell that is destined to contribute to the iris of the eye come to possess just the right set of transcription factors, to ensure that the genes for making an iris (and not genes for making a retina, or lens, or cornea) are expressed at just the right levels and at just the right levels and at just the right time as the embryo develops In other words, how do difference cells come to possess different transcription factors?” Answer looking at flies: “One principle is that the fly egg, even before it ever sees a sperm, is already subdivided into specialized areas: one end will give rise to the head, the other end to the tail; one part will become the top of the fly, another part the bottom…A second principal is that different genes respond to different amounts of a transcription factor…A third principle is that cells talk to one another, and these conversatins influence which genes get expressed, much as conversations in the hall of a high school influence who is going to the prom with whom.”

“By means of these intercellular conversations cells continually refine the set of transcription factor genes they express, ultimately causing them to express the specific set of genes that results in their taking on very specific functions.”

“It’s now almost as easy to find and copy genes as it is to find and copy passages from a book. The first step is to chop all the chromosomes into small pieces, which can be accomplished by adding to the chromosomes enzymes that cut DNA…They recognize specific short sequences of bases in DNA and cut wherever those sequences occur, producing a discrete set of fragments.”

“All cells have such a DNA joining enzymes because they constantly need to unite pieces of DNA to repair the damage that DNA continually incurs.”

“Many processes have to go right for gene therapy to work, and scientists are still a long way from having a failure-proof procedure. For gene therapy to work, biologists need to deliver the viruses carrying the therapeutic genes to the appropriate cells, where the good gene can do its job. Discoveries of how cells specialize in certain tasks have led to improvements in this cell targeting. Even if the good gene gets to the right cells, it must get turned on at the right time and at the right level to provide cells with the right amount of the protein they are missing, when it is needed. Furthermore, expression of that gene must persist for long periods of time, so understanding how transcription factors and other proteins determine whether a gene is on or off is invaluable.”

“Given its few successes and its several failures and tragedies, gene therapy has yet to live up to its much-ballyhooed potential. There are still enormous challenges in getting functional versions of genes into the right cells and, once there, getting them to produce an appropriate amount of the needed proteins for long periods of time.”

“Siblings of diabetics have a much higher risk of developing the disease than does the general population, and the identical twin of a diabetic—who shares her identical personal DNA code—is affected much more often than is a fraternal twin, wo has a different personal DNA code.”

“Although scientists can now analyze individual sperm cells and determine whether the Huntington’s disease gene in them is the normal or abnormal version, to an egg cell the billions of sperm are indistinguishable. The decisive event of fertilization is random, one of the many accidents of the universe we inhabit.”

“We don’t know which of Rita Hayworth’s genes suffered that fateful mutation—perhaps it was one of the presenilin genes—but it’s likely that a change in only one of her 6 billion base pairs led to the buildup of the amyloid-beta that shortened her dazzling career and prematurely ended her life.”

“How much of our temperament is due to our genes?…The answer is: both. Nature and nurture, our genetic endowment and our life situation and experiences, determine our behavior.”

“Estimating the genetic component of human behaviors and psychiatric disorders may help to remove a lingering stigma attached to people with mental illness—a misplaced sense that these are character flaws—and it may inspire more people to seek treatment. In addition, these studies all point to environmental components—generally still to b teased out—that interact with the genetic ones. That’s good news, since we have some control over the environmental inputs to disease. It is notable that even for the most heritable illnesses, such as schizophrenia or bipolar disorder, the heritability is never 100 percent, and even identical twins are never 100 percent concordant. Thus, even when genetics has a strong effect, it is not absolutely deterministic, so hope should never be abandoned.”

“The DNA codes of any two people are about 99.9 percent identical. For every 1000 base-pairs of DNA, only a single one will be different…How can such little difference in our personal DNA codes lead to such an enormous diversity of physical characteristics? This is one of the major unanswered question in biology.”

“A misincorporated base happens perhaps once in every five million to ten million base-pairs copied. Nearly all—99.9 percent- of the mismatches get fixed by the highly efficient mismatch repair machinery. A few of them—about one in a thousand—slip by and become the mutations we have been talking about.”

“In the 150 years since the theory of evolution by natural selection…the variation was changes in DNA, the mutations that affect genes and, ultimately, the proteins they encode (something Wallace and Darwin could not have known). Most of those mutations have no effect of the fitness of the individual and therefore don’t contribute to the evolution of species. Some of them reduce the fitness of an individual and get eliminated from the population. Every once in a while a mutation results in a change in the function of a critical protein in a way that makes the individual better able to compete with its peers for resources, leading to the spread of the mutation through the population with every generation. Eventually, most individuals carry that mutation, and the trait it confers on them then predominates. The population has evolved.”

“All organisms on the planet are built from the same set of genes. That’s because, way back when, we all had the same ancestor. Its name was LUCA—for “last universal common ancestor” of all living things—and it lived around three and a half billion years ago”.

“So we’re just going to have to accept it: our genes, which encode our proteins, are not all that different from those of the fly…”

“Natural selection—“survival of the fittest”—is an easy concept to grasp. And one hundred fifty years of research by many thousands of scientists have generated evidence to support the validity of the hypotheses beyond any shadow of doubt. Why, then, is the issue still so controversial? We honestly don’t know why. Perhaps it’s because the notion of evolution conflicts with the view that many held in Darwin’s time and that some still hold today: that God created living things just as they are today.”

 

 

 

 

 

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About hansston

Pastor a church in Sparta.
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