Chromosome 5 is where the asthma gene is located. Asthma affects many people worldwide, especially children. Much research has been done to assess the causes or factors that contribute to asthmatic symptoms. However, Ridley later explains that environmental factors that surround the individual are responsible for asthma. People who live in urban areas are more prone to have , but the interesting thing is that Urban areas are also fairly clean. Interesting enough, people who actually keep themselves clean have a higher chance of having asthma. Biologically, people's immune systems are constantly ready to encounter mycobacteria that is found in dirt or soil. In fact, the immune system needs these mycobacteria in order to keep occupied. Essentially, if a person does not encounter dirt often and is constantly clean, the immune system will be unbalanced and prone to asthma. In the end, unnatural pollution can lead to asthma, but constantly being clean in a sanitized environment can also lead to asthma.
Chapter 6
In the past three chapters, Matt Ridley would talk quite a bit regarding diseases and how certain genes in each chromosome may cause these diseases. Well he just wanted to make it clear that "Genes are not there to cause diseases." In fact, he mentions that genes are not even broken when they cause these diseases; they are just coded differently, just clarifying.
Chromosome 6 is the chromosome where intelligence is inherited. In 1997, Robert Plomin and his colleagues were proud to announce they found the source of intelligence, which is indeed a proud thing to say. What they did gather intelligent children from across the United States and search their blood for intelligence. This sounds utterly ridiculous, but in the end, they found something. On chromosome 6, there was a unique sequence that was not common among the majority of people; only the clever ones. The sequence is found on a gene called IGF2R.
IQ tests have been around for some time and it's not surprising that Ridley would find them absurd. As he mentioned, an IQ test is a test of random question and is graded not based on how well, but how fast. Can brilliance really be determined by time?
A man named H. H. Goddard took the test and then applied it to others, specifically immigrants. Essentially, this man was being racist against saying their IQ would not be sufficient based of his idea of what intelligence is. Eventually, he was given permission to test millions of soldiers during World War I which lead to classification. The United States Congress later passed an Immigration Restriction Act utilizing the test as an excuse to prejudge. Ridley concludes by saying, "IQ tests are inherently biased towards certain kinds of minds." Basically, IQ test results need to consider all the facts regarding the person's education, character, and the way they react to their surrounds. Also, by looking at test result similarities between family will influence someone's score as well. An IQ can not be simply determined.
Chapter 7
Ridley has talked about many different genes and chromosomes so far in Genome, but the questions remains, are human behavior or instinct involved with chromosomes? Ridley begins this chapter by boldly stating that chromosome seven has a gene that is responsible for instinct, and he is prepared to explain. Over a period of time, determinists have developed this idea that people have no control over theoretical behaviors, but Ridley proposes the idea that in reality, genes regulate human instincts from birth. This proposition is best proven through the data scientist have gathered regarding premature children grammar and development. Children are born into this world and have to attend school in order to obtain the amount of knowledge needed in daily life. Children, before school, during their first couple years are taught basic vocabulary skills which doesn’t come naturally, however, it has been determined that grammar is already well known to the average child. Was the child taught grammar prior? Apparently not. A linguistic known as Noam Chomsky proved this fact by arguing that human language is influenced by instinct just as much as cultural interaction. His research is recorded in his book, Syntactic Structures.
As the chapter continues, Ridley begins talking about how languages are affected by instincts, as well as language deficiencies. There is a gene that is directly located on chromosome seven that can cause damage in the brain which results in a linguistic disability. The gene in question is called SLI, which stands for Specific Language Impairment. The SLI gene causes people to become disadvantaged when learning grammatical skills, however this specific gene is significant because it is inherited. Scientists have had debates determining what exactly the SLI gene does and why. A family was studied in which certain members had the defect and others did not. The truth behind the gene is that it does not prevent people from learning, it just prevents natural grammar skills. Overall, chromosome seven does indeed affect natural instincts.
Chapter 8
Intermission, it is time to talk about chromosomes X and Y. After previously talking about how linguistics and instincts being affected by genes, it has now been confirmed that maybe the individual does not have full control over one’s own identity. Ridley begins the chapter by saying chromosome X is the next largest chromosome after number seven and is sometimes paired up with chromosome Y, which is extremely tiny. The XY combination is always exhibited in male organisms, while a double XX pair will result in a female. Essentially, the XY chromosomes are both sex chromosomes that are responsible for determining one’s sex.
Essentially, during development, everyone gets an X chromosome, and the only way for a male to exist is if it inherits the Y chromosome from their father. Thus, if the X chromosome is inherited from the father, the child is automatically a female. Other research has proven that because males only have one X chromosome, they are most likely to suffer recessive issues. For instance, if a guy’s X chromosome malfunctions, it’s all over, but if a female’s X chromosome malfunctions, at least they have another on standby.
As the chapter progressives, Ridley begins to dive into the importance of the X and Y chromosome and how it maintains a balance among species. He mentions that the Y-chromosomes has genes that provide masculine features while two sets of X provide feminine features. The DAX gene is located on the X and the SRY gene is located on the Y, which determines the sex. However, it has also been noted that sometimes these genes can become antagonistic towards each other resulting in malfunction. These types of scenarios can result in putting species in jeopardy. There must be a balance of males and females, or else they will die out. It is extremely important for the X and Y chromosomes to stay intact.
Chapter 9
There are four different blood types in the world for humans: A, B, AB, and O; each with a variation. As Matt Ridley opens up Chapter 9, he first states that Chromosome nine in the Human Genome has a gene that determines what blood type a person may have. As Ridley puts it, "it determines your ABO group." Not only does a person's blood group determine bodily functions, but it has also been used for evidence in court cases before DNA fingerprinting was implemented. Blood that is tested is presumably able to determine one's innocence, but this also means blood can identify people and relations. However, DNA tests are much more effective, thus blood groups today are used for transfusion in order to save lives.
The ABO blood systems were discovered in 1900, and after several attempts, received the titles of A, B, AB, and O, which was considered universal. It was discovered later that although transfusions do indeed treat a patient, mixing two different blood types end in disasters. The rule is that A can donated to other A's or AB; people with B can donated to B or AB; and O is universal. The breakdown is roughly as follows: 40% of Europeans have O, 40% have A, and 15% have B. This statistic is similar in other countries, except Native Americans, who are almost blood type A, and Eskimos, who were either B or AB.
When it comes down to a molecular scale, the ABO blood group gene is made up of 1,062 letters scattered across the chromosome. It's clear this is the Chromosome's main purpose of existence. A and B have a seven letter difference in which three don't change anything, while the other four define the separation in blood systems. Surprisingly, unlike the A group, the O group's only difference is the deletion of the 258th letter out of the original 1,062. This causes a frame-shift mutation in which everything after that 258th letter is moved over by one rendering the sequence as meaningless. However, people with O blood are not disadvantaged at all, this blood group does not seem to be connected with anything. In reality, it has been proven that people with certain blood types are more immune to diseases than others, so blood type may have a mysterious immunity for some and a vulnerability for others.
According to scientific data, Cholera has always had a serious effect on people with type O. They are immensely susceptible to infection. On the other hand, AB blood types are practically immune to cholera entirely; they will not have diarrhea from cholera infections. This severally attacks natural selection because according to the theory, the vulnerable blood type would die out. Obviously, they have not. As for O type people, although they are vulnerable to Cholera, they are more immune to other diseases like malaria or even cancer. Thus, each blood type has their advantages and disadvantages, which results in a balance of life.
Chapter 10
Everyone has stress, it comes hand in hand with life, but could it be that chromosomes are involved with stress? Well, Ridley titles his chapter on chromosome 10 of the human genome "Stress". In the beginning of the chapter, Ridley states, "The Brain, the Body, and the Genome are locked, all three in a dance." Cholesterol is an ingredient essential to the body, which is manufactured from sugars, but it is also responsible for creating steroids known as progesterone, aldosterone, cortisol, testosterone, and oestradiol. However, in order to convert cholesterol into steroids, the CYP17 gene located on chromosome 10 is necessary. Specifically, the CYP17 gene creates cortisol, testosterone, and oestradiol. Thus if this gene was not present, the only proteins that could be made are progesterone and aldosterone. This causes a defect in sex hormones so the subject does not experience puberty. Notably, Cortisol created by the CYP17 gene is responsible for syncing the body and brain, but if there is an overflow of Cortisol, a person is under stress.
Cortisol is a steroid with many purposes, but it is also directly linked with immune systems. It has been proven that people who experience stress (an overflow of cortisol) caused by an outside source are prone to get sick. Essentially, the steroid switches genes on and off which then go on to trigger other genes which then trigger more genes. The effects of Cortisol could involve hundreds of genes. "The main purpose of genes in the human genome is regulating the expression of other genes in the genome." Ridley imposes a question that deals with the nature of stress and the overseer of our genes, "Who's in charge?" A valid question with a complex answer. What orders the brain to release Cortisol and cause stress? Stress is caused by an outside source such as a difficult exam which then processed by the brain. The brain goes on to release adrenaline and make the cortisol active. However, the brain doesn't decide that an exam is a reason to cause stress since it cannot connect with the outside world. Also, everyone has different levels of stress which must mean they have differences in their genes, but that still doesn't answer the question. Ridley proposes that nobody is in control and that the world is simply too complicated. Stress is caused by many outside influences and it is unknown why the brain reacts the way it does. Towards the end, Ridley talks about how people who have lost their jobs end up getting ill due to stress levels, not because they were unhealthy. It's amazing how stress is clearly intertwined with the immune system due to the effects of steroids released by the brain. Although Cortisol was the steroid in question, it is also noted that Testosterone also has a connection with the immune system. However, once again, Ridley concludes without an answer to the reason why steroids that stimulate stress are linked to the immune system.
Chapter 11
Personalities, are they really determined by genes? So far, in Genome, Ridley has talked a lot about how genes affect people in ways that define who they are, but at the same time, he realizes that people are unique. Everyone has different feelings, stress levels, physical needs, and physical abilities. This is what gives people an individual element in their character. However, there is a gene that regulates personality which so happens to be located on Chromosome 11 known as D4DR.
The D4DR gene contains a recipe that has the ability to create a protein known as a dopamine receptor which is activated in some locations on the brain. The purpose of the protein is to catch Dopamine charges on the outside of the brain thus creating an electronic signal of its own. The brain uses electrical signals in order to stimulate chemical reactions creating physical actions. This also allows the brain to do several things at once such as type this document, inhale oxygen, think, pump blood, and operate internal organs. However, the Dopamine proteins also control motivation. For instance, an excess of dopamine can cause schizophrenia and hallucinogenic drugs stimulate dopamine for its main purpose as well as cocaine. Too much Dopamine can influence people to seek more adventurous lives, or too little can cause lack of motivation such as people with Parkinson's disease. In the mid 1990's, a scientist named Dean Hamer was seeking a gene that caused thrill-seeking personalities, but he knew it wouldn't just be a single gene. The first discovery was found by scientist Richard Ebstein within the D4DR gene. He discovered a sequence of 48 letters that were repeating two to eleven times. Depending on how many times this sequence repeats depends on how effective Dopamine receptors can be. The longer it is, the less responsive; the shorter it is, the more responsive.
Based off Ebstein's discovery, Hamer wanted to observe whether people with long D4DR genes have different personalities than those with shorter ones. However, his research didnt lead far because there was not an exact correlation. After further research among different groups of people, Hamer concluded 4% of novelty seekers were in correlation to the D4DR gene and the other 36% of people were considered heritable or influenced by environmental factors. There could be well over 500 possible genes that influence personality. As Ridley moves into the discussion of depression, it is also noted that cholesterol and serotonin levels have a similar effect to the Dopamine protein. People with lower levels have depression or violent actions, but this still does not indicate that genes regulate people.
Chapter 12
The miracle of life is a remarkable system in the eyes of a biologist. The idea that an egg can be fertilized to become a completely new being is extraordinary, and as Ridley puts it, "we must leave such a comfortable terrain behind and step into the unknown." From the beginning, Ridley refuses to discuss Divine Intervention, but continues by stating that the plan is contained within the egg through genes. Within Chromosome 12, there is a cluster of development genes that contain the codes necessary to create a brand new living organism. The process begins through fertilization which results in an embryo with a front and back. In fruit flies and toad, there are specific instructions for one end of the embryo blob to become a head and the other to become the rear. However, mice and humans develop those traits later through unknown means.
As cells develop, they obtain a sense of where they are located, but then have to begin construction. Genes that control this process are called Homeotic genes. Cells that know where they are can receive information from the genes they hold that tells them what to become whether it is an arm, kidney, or lung. This is all done through the process of genes switching each other on which eventually results in physical development. Every cell contains a copy of the genome thus giving them the ability to begin their work without waiting for a signal, it just all happens.
In the late 1970's two scientist named Jani Nusslein- Volhard and Eric Wieschaus were working in Germany studying the effects of mutant fruit flies. They were examining if X- Rays would cause mutations in the fruit fly embryos during development, which is exactly what happened. Fruit Flies would grow body parts in places that would cause them to be deformed, such as a a leg in an antenna spot. By dividing the mutation types, they discovered a pattern. "Gap Genes" defined whole areas of the body, "Pair Rule Genes" subdivided areas and defined finer detail, and " Segment- Polarity Genes" that subdivided details in the front or rear sections. Basically, this all means that the embryo is developed not by sections, but by a grand plan provided by the genes.
After Ridley continues in the chapter, he talks about how Hox Genes affect the development of species in both mice and flies, however, towards the end he asks," why are hox genes laid end to end, with the first genes expressed at the head of the animal, in every species so far investigated?" This was the first topic mentioned in the chapter. Apparently, there is not an answer to why an animal grows from bow to stern, it has just happened to be that way since its evolutionary roots. The hox genes have always begun this way and still do today.
Chapter 13
Everything since the beginning of time has been made up of what people know as history, and the origins of why things are the way they are. Ridley begins the chapter by saying, "DNA is a code written in a single alphabet- a language." Ridley uses the analogy of the Molecular Language to talk about how all languages that exist today all come of a common ancestry. Italian, French, Spanish, and Romanian all share word roots from Latin, which was one of the examples provided.
In 1786, Sir William Jones made an announcement to the meeting of the Royal Asiatic Society regarding a discovery he made. The Indian language of Sanskrit was related to Latin and Greek. He also discovered a similar comparison between Celtic, Gothic, and Persian. So many similar languages scattered across the globe can only mean a common source. Basically, everyone on the earth spoke one language, and as people spread, the languages became diverse resulting in today's modern languages. Ridley goes on to explain to research conducted to confirm migration in the Europe-Asia Region. In Turkey, the people during this time were farmers who had words for crops, cows, dogs, ect. This was all dated just after the invention of agriculture in the Syria and Mesopotamia region, so technological advances influenced their language. Due to the location, this language with all these new words for agriculture soon spread through different continents and diversities. In Anatolia, people speak Turkish due to horse riding warriors that migrated into the area from central Asia. The Altaic people were already familiar with Horses since they had several words in their language meaning horse. Ridley then moves onto the Uralic language spoken in Northern Russia, Finland, Estonia, and Hungary which also contains trances of successful human migration from the Indo- Europeans because they started herding domestic animals as well. Basically, these three families of languages all originated about 15,000 years beforehand when it was a single language used by hunters.
In the 1980's, a scientist named Luigi Lua Cavalli-Sforza was researching whether or not linguistic boundaries coincide with genetic boundaries. Obviously, the difference in genes is less than the difference in language, but there is a common pattern discovered through data. The data is known as the five contour maps, which has shown the spread of gene frequencies everywhere throughout Europe. This essentially results in the discovery that human migrations and expansions of people with "novel technological skills" may indeed have a role in the theory of evolution. Ridley moves on to discuss the effects of foreign marriage in Finland as a means of linguistic diversities being spread. Apparently, Finland males have a special Y chromosome that is different from the rest of Europe, but actually similar to Y-chromosomes in Northern Asia. This essentially means that the Uralic language and Y chromosome was introduced into the Indo-European population. Ridley then realizes that he has not talked about chromosome 13, but he quickly begins by saying there is a gene that hold genealogy known as BRCA2. The BRCA2 gene was discovered in 1994 as a "breast cancer gene", but this only occurs if there is a mutation in the letters. The deletion of five letters after the 999th term can cause breast cancer, but it is rare. However, further down the line, a deletion of the 6,174th term can also cause breast cancer, but is commonly found in people of Ashkenazi Jewish decent. A closer to look at the problem shows that interbreeding is the leading cause to this specific mutation, which was commonly found in Iceland's history. This would explain why Iceland has a high rate of people with Breast Cancer.
Chapter 14
Everyone knows that the body grows old and eventually dies, this is the unfortunate fate. Interestingly though, Ridley names chapter 14 of Genome Immortality as if the body has the ability to regenerate itself continuously. Although people cannot be immortal, there is a reason behind the title. Ridley begins by discussing the development of humans. Essentially, the embryo of a human will constantly divide itself by doubling. It starts with one, then two, then four, than eight, and it just keeps going until it reaches the trillions of cells necessary. Amazingly, it only takes about forty-seven doubling. However, it should also be noted that because the genes are constantly being copied, eventually they grow old. Chromosome 14 is the home of a gene known as TEP1 which is responsible for manufacturing a protein know as telomerase. Leading back to the title of the chapter, the telomerase protein is actually capable of making certain cells completely immortal which seems extraordinary. However, the lack of telomerase essentially causes the process of deterioration over time; otherwise known as growing old.
Chapter 15
In 1972, co-discoverer of DNA, James Watson, was studying DNA copying polymerases and discovered that they do not start the duplication process from the beginning of the sequence. The polymerases will literally indent and begin coding from there, which means that random nonsense in the beginning is necessary to ensure all the proper letters in the sequence are coded after the indent. The random sequence in humans is TTAGGG repeated around two thousand times afterwards. The official name of this rubbish sequence is called telomere, which prevents the DNA from being cut short. However, constant duplication leaves a bit of telomere behind which after a while could render the sequence useless. The consequence of duplication is that eventually, it runs out of usable material.
In 1984, the telomerase protein was discovered by Carol Greider and Elizabeth Blackburn. This amazing discovery allowed scientist to learn that telomerase actually has the sole purpose of repairing the damaged telomeres after being duplicated so many times, thus allowing cells to continue copying. Telomerase consists of RNA, which serves as a template for reconstruction. To scientist, this is telomerase is extremely significant because it contains the universal telomere template: TTAGGG. The only creatures that lack this similarity are called ciliate protozoans which contain the sequence TTTTGGGG or TTGGGG. Ridley believes they may have originated from Luca herself because they do not fit in with the rest of life.
TEP1 gene that codes for telomerase serves the body as a means of an elixir for immortal cells. Although they cannot create eternal youthfulness, telomerase is currently being researched as a means for curing cancer. In the body, telomerase genes are switched off after development, but if switched on again, it could cause tumors leading to cancer. This is what the malignant tumor does in order to grow. Lack of telomerase still causes cells to grow old and die; however, the body itself can live without it. Cells duplicate and die, it is the natural order, and it has later been discovered that the reason for aging is actually due to the accumulation of expired cells. In conclusion, the age of a person is in direct correlation with the chance of getting cancer because cells go through an immense amount of cell division over time.
Genetics is the study of the characteristics and traits an offspring has once they are born. The father and mother have dominant and recessive genes that determine what traits are exhibited based on the punnett square. However, Matt Ridley first begins his chapter on chromosome 15 by discussing two diseases, Prader-Willi Syndrome and Angleman Syndrome which later tie in with parental inheritance. Prader-Willi Sydrome was first discovered in 1956 by Swiss Doctors and begins at childbirth. Children born with this rare disease have floppy and pale skin, refuse to drink breast milk, and can never be satisfied when eating till they almost burst. The result, of course, is obesity once they grow older, and it noted that they may be mildly mentally retarded. This syndrome also causes underdeveloped hands, feet, and sex organs. This is an inherited disease due to genetic mutation, and surprisingly, families known to have Prader-Willi Syndrome have a higher chance of Angleman Syndrome as well. Angelman Syndrome is essentially the opposite of the previous disease because it causes children to be born abnormally skinny. The people with this disease are thin, hyperactive, and insomniac, small headed, long jawed, and have large tongues. Interesting enough, both of these diseases are caused by missing chunks within chromosome 15. Chromosome 15 consists of eight genes in total, and if the UBE3A gene is broken, a child could have Angleman syndrome. If the SNRPN gene is broken, the child could have Prader Willi syndrome. However, depending on which parent the missing chunk of the chromosome came from, would determine which disease a child ends up receiving. If it came from the father, the child would have Prader-Willi Syndrome, and if it came from the mother, the child would have Angelman Syndrome.
It would seem based on this conclusion, that the genome contains genes with maternal imprints that defines which parent it came from. If that specific gene from either parent is active, than the imprint for that parent will be switched on and the other off. In the late 1980’s, two groups of scientist conducted research to see whether it was possible to have a uniparental mouse. They would take the chromosomes from a female egg and inject it into a fertilized egg that had the sperm pronuclei extracted. The same could be done the other way around, thus there could be either two mothers or two fathers depending on what procedure was conducted. However, the embryo died because it lacked what was needed from both parents, specific genes. Parental genes from the father make the placenta and the maternal genes from the mother make most of the embryo including the brain and head. Ridley notes that imprinted genes such as these may explain why we inherit certain behaviors from parents. According to the previous information, the offspring should have a mind like their mother and the moods like their father. It is also noted that gender, male or female, is genetic and that is the reason for diversity between the two. It was proven in 1997 after an experiment conducted on a boy named John, that being a man or women is not defined by social or environmental aspects, but solely genetic.
Chapter 16
The Human Genome is basically the entity of a human being and the regulator of the body. It simply works on its own without having to train a brain to think or a heart to beat. As Ridley begins this new chapter, he states that Chromosome 16 is the home of the body’s delegator genes that are responsible for learning and memory capabilities. Human beings have the amazing skill of storing information we receive in the real world and keep it stored away in the brain for further use if necessary. However, the question is, what is the difference between already present knowledge and learning? Instinct is the word Ridley uses, and defines it as genetically determined behavior. Whereas learning is behavior modified by experience. Two completely different types of knowledge that are independent, but what determines the category? As mentioned before in previous chapters, language is an instinct that comes naturally, but people have learned to develop different dialects and vocabulary based on social influences. What caused this? Ridley begins talking about a man named James Mark Baldwin that wrote an article in 1896 discussing this topic. Essentially, instinct gives humans the ability to do things that animals do, such as walk stand, and blink. Nonetheless, the ability to learn allows humans to expand on top of what animals can do to fit certain needs such as fit into a civilized society. “The main function of consciousness is to enable [the child] to learn things which natural heredity fails to transmit.” Ridley ends this point by saying natural selection essentially left the book of life open for suggestions. The reason why basic language skills is instinct and vocabulary learned is to allow words evolve with time. Natural Selection does not have the capability of establishing something that cannot be modified, thus vocabulary will continue to change.
Instinct is necessary, but learning to adapt or accomplish new tasks is just as essential. Experiments performed by Eric Kandel proved that other animals such as bumblebees, sea slugs, and dogs can learn just as well as humans. The three different types of habituation, sensitization, and associative learning. Looking deeper into the brain, it is clear that there is a specific chemical that allows the brain to learn which is called AMP found in neurons. However, the brain itself is made of genes, thus the genetic code is responsible for the ability to learn and remember.
Chapter 17
The chapter dedicated to Chromosome 17 is titled death, as this chromosome causes death. However, Ridley begins his analysis of the chromosome by talking about cancer. The cells within a human body are destined to serve a purpose, however mutiny can occur. Cells are instinctually called to divide continuously until a switcher shuts them off. Nonetheless, if a cell refuses to stop reproducing, the result is known as cancer. The genome has created a special kind of switcher that makes a cell commit suicide if it were to become cancerous. The switcher is called TP53 and is located on the short arm of Chromosome 17. Genes that prevent cell duplication are called tumor-suppressor genes, and genes that encourage cell reproduction are called oncogenes. Cells must divide for the body to survive, but an over abundance is deadly, so tumor-suppressor genes create a balance. Thus if oncogenes or src genes are not regulated, they could cause cancer. It’s interesting to note that based on this information, genes are the cause for cancer. In 1975, scientist refused that this was a genetic disease because it was not always inherited. However, cancer itself could exist within the body and not touch reproductive organs, thus cancer would affect the host, but not the offspring. Cancer is genetic.
Referring back to TP53, which is located on Chromosome 17, is the gene that creates a protein called p53. This is the protein that is responsible for halting cell duplication or ordering the cell to commit suicide and is even in clinical trial to one day become a drug. However in many cases of cancer, the TP53 gene has already been mutated before the issue can be prevented. The cure for cancer is to stop cells from growing, however, if the TP53 gene is already mutated, than Chemotherapy or radiation will not be as effective.
As Ridley closes this chapter regarding death and cancer, he begins talking about the evolutionary life of cells. Cells will naturally do what needs to be done for the good of the entire body. If a cell is defective, it will kill itself. As Ridley puts it, “We are stuck with the cell-suicide mechanism we inherited.”
Chapter 18
In contrast to the previous chapter, Ridley decides to title his chapter of Chromosome 18 as Cure. Although there are many murderous diseases that lack cures, scientific research is constantly being conducted to solve the mysteries of the micro bacterial world. Some are truly brilliant, some could use reconsideration, and others should not be thrown away if at first it does not succeed. However, when dealing with editing the genetic code of life, things can get complicated. As Ridley first states, “It [The Genetic Code] is no longer a precious manuscript; it is on a disk. We can cut bits out, add bits in, rearrange paragraph, or write over word.” It sounds like science is progressing rapidly, but is changing the genetic code wise or ethical?
Chromosome 18, in connection with the previous chapter, has a tumor-suppressor gene that works to prevent colon cancer. This gene’s location and name was previously unknown, and was thought to be some other gene called DCC. However, scientists do know that if a child is born with a defective version of the gene, their cancer risk increases. Ridley uses this example of a defective gene to discuss genetic engineering in more detail. Apparently, it is possible to remove a faulty gene such as the one mentioned and replace it with a working gene, thus curing the patient.
Coincidentally, the same way people cut paper with scissors and reattached with glue is the same basic principal for genetic engineering. Biologically, Scissors are known as restriction enzymes and glue ligase enzymes. Both enzymes work with DNA by cutting bits out and placing new bits in. However, this only works when they find a specific sequence in the chain. In 1972, scientist Paul Berg from Stanford conducted an experiment that successfully chopped a piece of DNA in half and reattached it in a different order, thus the first man made “recombinant” DNA sequence. This breakthrough in science was revolutionary, but brought public concern. In 1975, scientist gathered together to discuss the policies of genetic engineering so that it is safe and follows federal codes. Soon Biotech companies began production.
It’s one thing to experiment “recombinant” DNA on bacteria, but it is much more complicated to insert a gene as a replacement into the human genome that consists of 100 trillion cells. The DNA would have to be inserted into every cell to take effect, however in the 1970’s it was discovered that retroviruses can actually take the modified DNA and spread it around the body. Retroviruses could work, but could also cause safety issues within human beings, thus scientist agreed human genetic engineering was premature. The technology is still being perfected, but one day, recombinant DNA could be the cure to countless genetic problems or diseases.
Chapter 19
Information is power, and it just depends on how it is used. When developing medications or ways of preventing illness, a scientist must consider the importance of the final product. If the medication fails, the lives will not be saved. The way Ridley puts it, “Because something can be done, it must be done.” Brilliant quote regarding the significant of scientific discovery and innovation to help save lives. Ridley begins the chapter dedicated to chromosome 19 by introducing two killer diseases: Alzheimer's disease and coronary heart disease.
The Apolipoprotein genes, or otherwise called APO, have four varieties: A, B, C, and E. Each version rests on a different chromosome, however, APOE lies on chromosome 19 and is the gene of focus. There is a protein within the blood stream, lipoprotein, that acts as a delivery truck for cholesterol. When the protein has a delivery to make, it needs a receptor that tells it which cell to drop of the delivery. APOE acts as that very receptor, almost like an address, and APOB helps with the drop of. If both of these APO genes were to stop working, cholesterol will build up in the bloodstream without a place to be delivered, thus heart disease would occur. Luckily the APOE gene has different variation in which test can be conducted to determine whether a person is prone to have a heart disease. Ridley uses Europe statistics as the example. In Europe, more than 80% of people have a copy of E3 which is the best and most common form of APOE; less risk of heart disease. However, 7% of people have a copy of E4 which puts them in a high risk zone for heart disease. Finally, 4% of people have a copy of E2 which make the patient prone to heart disease, but is treatable. Conducting tests to determine your level of risk can help prevent heart disease.
When dealing with Alzheimer's disease, it’s interesting to note that it is also connected with the APOE gene, but more specifically the E4 variation that causes heart disease. Alzheimer's disease causes the patient to eventually lose all their memory with time and is very unpleasant. Apparently, patients also seem to have high cholesterol which may be in part to the APOE gene not working properly. Thus, the buildup in plaque throughout the bloodstream affected the brain just as bad. However, Ridley notes that the same form of tests used for heart disease can be used for Alzheimer's disease. Although it is incurable, it will let the patient know what they have despite the inevitable.
Chapter 20
“Before the discovery of the Genome, we did not know there was a document at the heart of every cell three billion letters long of whose content we knew nothing”. - Matt Ridley
The Human Genome becomes more fascinating per chapter primarily due to the abundance of unanswered questions about it. Which is perfect since this chapter is not only dedicated to chromosome 20, but mystery as well. There is a gene called PRP that lies on chromosome 20 that scientist have been unable to figure out, but have won nobel prizes just for discovering it’s existence. It would also become a political issue in science in the year 1996. What is this gene and why is it a mystery? Ridley continues.
Ridley begins by saying sheep, during the eighteenth century, became a revolutionized form of agriculture because owners were able to selectively breed them for desirable traits; genetics 101. However, sheep that were of the Suffolk breed began to develop irational behavior and soon became ill. They eventually died because of this unknown attack on their system, which would later be called Scrapie. The disease soon spread from the Suffolk breed to around the world. The disease wasn’t inherited but rather infectious, however microbes that were “supposed” to cause this brain disease was undiscoverable.
Time passes and there still is not an answer, however, an American scientist named Bill Hadlow noticed that the damaged brains of the sheep were strikingly similar to cases in Papua New Guinea. In a tribe known as Fore, people were stricken by a brain disease which killed many people, especially women. Through further investigation, it became apparent that the reason why women were mostly affected was because of a funeral ritual where the women would eat the dead. The disease was passed to them, thus the government ruled this ritual out.
As Ridley returns to discuss PRP, the qualities discovered are actually interesting to note. In 1982, a scientist named Stanley Prusiner discovered a protein that was found in scrapie-like animals and more importantly resisted digestion by protease enzymes. The gene was PRP which stands for protease resistant protein. The PRP gene is found in mice and humans, but the significant thing about it is that it produces a prion, a protein, that changes its shape to a tough and sticky form. It can not be destroyed and it changes other prions into versions of itself. As the chapter progresses, Ridley talks about the politics behind the scare of the Scrapie disease and the ridiculous methods attempted to prevent it. Many meat products were banned because the disease appeared to come from specific meat products.
