What is XYY syndrome?

Risk Factors

Only males are at risk for XYY syndrome. Most cases of the disorder are not inherited but result from a random event during the formation of sperm cells.

Etiology and Genetics

All normal human cells contain forty-six chromosomes consisting of twenty-three pairs; one member of each pair is contributed by the female parent and one by the male. Of these forty-six chromosomes, two chromosomes, designated X and Y, are known as the sex chromosome pair. Individuals with an XX pair are female, while those with an XY pair are male. Unlike the other twenty-two chromosome pairs, the X and Y chromosomes are strikingly different from each other in both size and function. While the Y chromosome is primarily concerned with maleness, the X chromosome contains information important to both genders.

During formation of sperm and eggs in the testes and ovaries, respectively, a unique form of nuclear division, known as meiosis (or reductional division), occurs during cell division that halves the chromosome number from forty-six to twenty-three. Sperm and eggs thus carry only one member of each pair of chromosomes, and the original number will be restored during fertilization. Because females have an XX pair, their eggs can have only an X chromosome, while males, having an XY pair, produce sperm bearing an X or a Y chromosome.

A common genetic error during sperm or egg production is known as nondisjunction, which is the improper division of chromosomes between the daughter cells. Nondisjunction in the production of either gamete can result, at fertilization, in embryos without the normal forty-six chromosomes. XYY syndrome is one of several of these aneuploid
conditions (possession of one or a few more or less than the normal number of chromosomes) that involve the sex chromosome pair. While Klinefelter syndrome (an XXY male) and Turner syndrome (an X female) are more widely studied and recognized genetic diseases, the XYY male occurs with a frequency of 1 in 1,000 male births in the United States, according to the National Institutes of Health. Caused by a YY-bearing sperm fertilizing a normal X-bearing egg, the XYY embryo develops along a seemingly normal route and, unlike most other sex chromosome diseases, is not apparent at birth. The only physical clue is unusually tall stature; otherwise, an affected male will be normal in appearance. The XYY male is also fertile, unlike those with aneuploidies involving other combinations of sex chromosomes, which usually result in sterility.

Symptoms

Boys with XYY syndrome are usually tall, have difficulties with language, and may have slightly lower intelligence quotients (IQs) than other members of their families. They may also develop learning disabilities, hyperactivity, attention deficit disorder, and minor behavioral disorders.

Interest in the association between aggression and the Y chromosome began in the years following World War II. Both psychologists and geneticists began intensive scrutiny of the genes that were located on the male sex chromosome. Men with multiple copies of the Y chromosome thus became the subjects of much of this research. Genetic links to violent, aggressive, and even criminal behavior were found, although many argued that below-average intelligence played a greater role. Many males with XYY syndrome do perform lower than average on standard intelligence tests and have a greater incidence of behavioral problems. The majority, however, lead normal lives and are indistinguishable from XY males.

The controversy surrounding this research began with a study at Harvard University that began in the early 1960s and ended in 1973 because of pressure from both public and scientific communities. The researchers screened all boys born at a Boston hospital, identifying those with sex chromosomal abnormalities. Because the parents of XYY boys were told of their children’s genetic makeup and the possibility of lower intelligence and bad behavior, critics claimed that the researchers had biased the parents against their sons, causing the parents to treat the children differently. The environment would thus play a greater role than genetics in their behavior. Subsequent research has shown that the original hypothesis is at least partially accurate. There is a disproportionately large number of XYY males in prison populations, and they are usually of subaverage intelligence compared to other prisoners. It must be emphasized, however, that the majority of XYY males show neither low intelligence nor criminal behavior.

Scientists, doctors, geneticists, and psychologists now agree that the extra Y chromosome does cause above-normal height, reading and math difficulties, and, in some cases, severe acne, but the explanation of the high prevalence of XYY men in prison populations has changed its focus from genes to environment. Large body size during childhood, adolescence, and early adulthood will no doubt cause people to treat these individuals differently, and they may in turn have learned to use their size defensively. Aggressive behavior, coupled with academic difficulties, may lead to further problems. Clearly, however, the majority of XYY males do well. The issue would be much easier to resolve if a YY or Y male existed, but because lack of an X chromosome results in spontaneous miscarriage, no YY or Y male embryo could ever survive.

Screening and Diagnosis

Identification of this disorder after a child is born requires that the child receive genetic testing or screening and is often discovered accidentally as a consequence of results from another genetic test. A pregnant woman’s cells can be examined by either amniocentesis or chorionic villus sampling to determine if her child will have XYY syndrome. In amniocentesis, a sample of cells is taken from the amniotic fluid; chorionic villus sampling examines cells in the placenta.

Treatment and Therapy

Men with XYY syndrome may require help in school to deal with learning disabilities and behavioral difficulties. Speech, physical, and occupational therapies can also prove beneficial. The support of family members is another important element in helping men cope with this disorder.

Prevention and Outcomes

There is no cure for XYY syndrome. However, help in school and a supportive family can reduce the educational and behavioral problems associated with the disorder. Most males with XYY syndrome lead normal lives.

Bibliography

Bryant, Daniel M., et al. "Sex Chromosomes and the Brain: A Study of Neuroanatomy in XYY Syndrome." Developmental Medicine & Child Neurology 54.12 (2012): 1149–56. Print.

Chen Harold. “XYY Syndrome.” Atlas of Genetic Diagnosis and Counseling. Totowa: Humana, 2006. Print.

Kim, Ina W., et al. "47 ,XYY an Male Infertility." Rev. in Urology 15.4 (2013): 188–96. Print.

Mader, Sylvia S. Human Reproductive Biology. 3d ed. Dubuque: McGraw-Hill Higher Education, 2005. Print.

Simpson, Joe Leigh, and Sherman Elias. “Sex Chromosomal Polysomies (47,XXY; 47,XYY; 47,XXX), Sex Reversed (46,XX) Males, and Disorders of the Male Reproductive Ducts.” Genetics in Obstetrics and Gynecology. 3d ed. Philadelphia: Saunders, 2003. Print.

Tamarin, Robert H. Principles of Genetics. Boston: McGraw-Hill, 2002. Print.

Templado, C., F. Vidal, and A Estop. "Aneuploidy in Human Spermatoza." Cytogenetic & Genome Research 133.2-4 (2011): 91–99. Print.

Vernice, Mirta, and Anna Cremante. “Life Span Development in XYY.” Life Span Development in Genetic Disorders: Behavioral and Neurobiological Aspects. New York: Nova Biomedical Books, 2008. Print.

Discuss Kurtz' last words in Heart of Darkness. What is their significance? How does Marlow interpret them?

Kurtz’s last words, “The horror! The horror!” have been widely debated by critics and could have multiple meanings. On the surface, it seems that he is referring to the horrors he has witnessed during his time working in the Congo. He is horrified with imperialism and the exploitation of African people and resources. It could also be that he is horrified with himself and what he has become. From the beginning of the novel, Marlow hints at the psychological changes that take place in a person when they travel into the “heart of darkness,” and it seems Kurtz may be horrified at the changes in his mind and the atrocities that has made him capable of. We can gather that Kurtz has been brought to a certain level of insanity from his experience in the Congo, and this could also be what he is referring to with his last words.

Marlow seems to see Kurtz’s last words as a dying man’s last moment of complete clarity before passing. Because Kurtz was able to have such poignant and revelatory last words, Marlow sees him as a “remarkable man.” Marlow is so impressed that Kurtz, on the edge of death, is able to say words that he believes encompasses some kind of great truth. Marlow says:

He had summed up-- he had judged. ‘The horror!’ He was a remarkable man. After all, this was the expression of some sort of belief; it had candor, it had conviction, it had a vibrating note of revolt in its whisper, it had the appalling face of a glimpsed truth-- the strange commingling of desire and hate.

Marlow finds Kurtz so remarkable because even in his last moments he is able to speak truthfully and with conviction- because his beliefs do not falter even in the weakest moment. It is not clear from this whether Marlow believes “the horror” refers to the exploitative acts of imperialism or whether it is Kurtz’s own soul, but it is clear that Marlow admires Kurtz because of them.

Where is Long Walk to Freedom: The Autobiography of Nelson Mandela set? What is the landscape like? What objects are part of the setting?

The book opens in 1918, the year of Mandela's birth, in rural South Africa. More specifically, the setting is the small village of Mvezo.

The narrator notes that Mvezo is a traditional and isolated village, set quite apart from the major events that were playing out in the world at large (most notably World War I, called The Great War here because, of course, people weren't expecting a second one at the time, as well as the terrible epidemic of the flu).

The landscape of this setting is beautiful, and as Mandela introduces it to us, he emphasizes its "rolling hills," its lush valleys, and its many, many "rivers and streams." Thanks to these flowing bodies of water, no matter what time of year it is, the landscape remains green. Mandela goes on to describe the whole region as "rich and temperate," possibly anticipating that many readers in the US will automatically and incorrectly equate Africa with barren deserts.

The lushness and beauty of the landscape might be best summarized by Mandela's recollection that his childhood fostered his "love of the veld, of open spaces, the simple beauties of nature, the clean line of the horizon."

When the story moves to the nearby village of Qunu, the general landscape remains green, grassy, hilly, and full of clear streams.

As for objects important to the setting, you might consider the oxen first. We infer that they are of great value, since Mandela recounts the story of his father being deposed from his political position due to "a complaint against him involving an ox that had strayed from its owner." Other important objects in the environment here include the clusters of huts, made of mud and shaped like beehives; the buckets used to bring water from the streams; the three-legged iron pot in which the narrator's mother prepared food; as well as the "cattle, sheep, goats, and horses" that graze the grassy pastures. The cattle seem to be especially important:

"I discovered the almost mystical attachment that the Xhosa have for cattle, not only as a source of food and wealth, but as a blessing from God and a source of happiness."

The thorn bush seems important, also, as an object in the environment, as it's the reason for Mandela's early shameful encounter with the donkey that so embarrassed him in front of his friends.

Finally, the one-room schoolhouse with the "western-style roof" also emerges as a crucial part of the setting, the place where, despite his mother's reluctance, Mandela first attends school.

What is one challenge that George Washington and the nation faced during his presidency?

One of the most significant challenges faced by the Washington Administration was the outbreak of war between France and Great Britain in 1793. While the wars of the French Revolution had been ongoing for more than two years at this point, Great Britain's declaration of war on France was significant because it raised the possibility that the United States might get dragged into the war. France hoped, due to a treaty with the United States, that the United States would side with them. But many Americans favored Great Britain, in particular wealthy merchants, and so Washington faced a great deal of foreign and domestic pressure on the issue. In response, he issued a proclamation of neutrality that affirmed the right of the United States to remain neutral in the conflict. Washington feared the new country would have been destroyed just a few years after its creation had it become involved in the war. Over time, this position was challenged by both Great Britain and France, as the navies of the belligerent nations attacked American ships that sought to maintain commercial relationships with each. The war became a major domestic political issue, as well, as many Americans overtly favored supporting the French, whose revolution espoused ideals not unlike those that motivated the American revolutionaries.

In the novel "The Swiss Family Robinson" what did the family have for breakfast the first day on the island?

On the day the family first land on the island, they do not eat first thing in the morning.  They get up, have morning prayers, and then load themselves and some animals and supplies into the raft of wooden tubs they have made.  This is described in Chapter Three.  

After landing on the island, they unload their vessel and make themselves a meal.  All this is described in Chapter Four.  The meal is soup, which they make from cubes of "portable soup" (i.e. bouillon) in a pot.  Having no bowls or spoons, they use oyster shells to scoop up the soup.  They cook the oysters in order to get the shells open, and the boys try swallowing the oyster meat, but do not like it.  It is also implied that they add some "biscuit" ... that is, hardtack. 

This is their first meal on the island, but it cannot be called breakfast, as it takes them all day to get it.  Shortly after they eat, the sun sets, and they bed down in their tent. 

Chapter Five describes the family's first morning on the island.  Their breakfast is biscuit, supplemented by meat from a lobster which ten-year-old Jack had caught the day before.  The oldest boy, Fritz, shares his biscuit and a claw of the lobster with the dogs to get them to trust him again, because he had beaten them the day before. 

What are neurons in biological psychology?

Introduction

In the latter part of the nineteenth century, there were two competing theoretical approaches toward explaining the composition of the brain. The reticular theory, championed by the Italian scientist Camillo Golgi
, proposed that the brain consisted of a dense, netlike structure of nerve wires with no individual cells. The neuron doctrine, as advocated by the Spanish scientist Santiago Ramón y Cajal
, asserted that the brain was composed of individual cells, just like other structures of the body, and that these cells were separated from one another by small gaps. The best microscopic views of that era could not provide evidence to determine which theory was correct, and a contentious debate ensued.

Ironically, it was a staining technique developed by Golgi in the late 1800s that enabled Ramón y Cajal eventually to demonstrate the existence of individual cells in the brain, confirming the neuron doctrine. Ramón y Cajal called these cells neurons, nerve cells that are specialized to receive information and electrochemically transmit it to other cells. In 1906, the gaps between these neurons were termed “synapses” by Charles Sherrington
, who deduced many of the properties of synaptic functioning.

Neuronal Structure and Types

There are an estimated one trillion neurons in the human nervous system, with somewhere around one hundred billion in the brain. Neurons share many of the same features as other cells. For example, they are surrounded by a membrane, have a nucleus that contains the chromosomes, are provided metabolic energy by mitochondria, and synthesize proteins at sites called ribosomes. What makes neurons structurally different from other cells is a unique tripartite structure.

Most neurons contain a soma, many dendrites, and only one axon. The soma or cell body is a rounded swelling of the neuron that contains the cell nucleus. Electrical messages, also called impulses or action potentials, are collected in the soma, which, in turn, may cause the discharge of electricity to another cell.

Input to the soma usually comes from dendrites. Most neurons have many of these branching fibers whose surface is lined with receptors specialized to receive impulses. Some dendrites have small outgrowths called spines, which increase the places available for connection to other cells.

The axon is a thin fiber, usually longer than the dendrites, that is specialized to send messages from the soma to other cells. Axons have many branches, each of which enlarges at the tip, forming the terminal end bulb. It is from this end bulb that chemicals are released into the synaptic cleft (gap).

Neurons can be distinguished from one another in several ways. Axonal length is long in projection neurons, but short or even absent in local neurons. The function of neurons is different in sensory neurons, which are specialized to detect physical information from the environment, and in motor neurons, which are specialized to activate muscles and glands. A third function of neurons, found in interneurons, is to communicate only with other neurons. The direction of the neural impulse is toward a structure in afferents, away from a structure in efferents, and within a structure in intrinsic neurons. Finally, neurons can be distinguished on the basis of polar dimensions. Unipolar neurons carry a message in one direction only, bipolar neurons convey an impulse in two directions, and multipolar neurons can transmit information in many directions.

The Resting Potential

Each neuron has the capability of producing an electrical charge called the resting potential. Neurons in their resting (nondischarging) state generate voltage by creating an imbalance of positive (sodium, potassium, and calcium) and negative (chloride) electrically charged particles called ions. Four factors contribute to this ion imbalance between the inside and the outside of the neuron’s membrane. First, the membranes of neurons have small gaps in them called ion channels. Potassium and chloride ions pass through these channels more readily than sodium ions, resulting in more negative ions on the inside of the neuron than on the outside. Second, the sodium-potassium pump forces three sodium ions out of the neuron for every two potassium ions allowed inside the cell, resulting in less positively charged ions inside the neuron. Third, proteins on the inside of the neuron carry a negative charge. Finally, the gradient balance between entropy—ions will move toward a place of less density—and enthalpy—ions will move toward a place of opposite electrical charge—results in a further negatively charged environment inside the neurons. Combining these four factors together yields approximately a −70 millivolt resting potential for each neuron. In other words, the neuron is like a battery that carries a charge of −70 millivolts.

The Action Potential

Stimulation from the environment or other neurons can disturb the balance that creates the neuron’s resting potential and produce a reversal of electrical polarity that leads the neuron to discharge an electrical impulse. This process is called the action potential and occurs in three phases. The first phase begins with a depolarization—a reduction of the electrical charge toward zero—of the neuron. When this depolarization is sufficient to cause the neuron to be approximately 10 to 15 millivolts less negative, the threshold of excitation is reached and the sodium ion gates, responding to the voltage change, will be opened. This results in a sudden influx of positively charged ions resulting in a reversal of polarity. One millisecond after the sodium gates open, they immediately shut, cutting off the sodium influx, and the gates cannot be opened for another millisecond or so, ending the first phase of the process.

The second phase begins with the opening of the potassium ion channels. Because the inside of the neuron is now positively charged and dense with potassium ions, the positively charged potassium ions flow out of the neuron. Unlike the sodium gates, the potassium gates do not snap shut quickly, and this results in fewer potassium ions inside the neuron than during the resting state. The net effect is that the second phase produces a hyperpolarization, which means that the neuron has an increased charge of approximately −110 millivolts.

In the third phase, the sodium and potassium gates return to their normal conditions, restoring the ion flow conditions that create the resting potential. As a result of the action potential, slightly more sodium ions and slightly fewer potassium ions are found in the neuron at the beginning of the third phase. The sodium-potassium pump eventually corrects this small imbalance and restores the original resting potential conditions.

Between the peak of the action potential and the restoration of the resting potential, the neuron resists generating an action potential. This resistance of refractory period is first absolute—it is impossible for an action potential to occur—and then relative—action potentials can happen, but require stronger-than-normal stimulation.

Axonal Conduction

In motor neurons, but not all interneurons or sensory neurons, the action potential begins where the axon exits the soma, a place called the axon hillock. Basically, each point along the axon regenerates the sodium-ion influx as it travels down the axon like a ripple caused by throwing a stone in a pond. Because the sodium-ion gates snap shut shortly after they open, the action potential will not travel back to the soma and the impulse is ensured to move toward the synapse. Unlike the small ripple on the pond, the traveling wave down the axon does not diminish in size or velocity and is independent of the size of the stimulus that generates it. This axonal (not dendritic or somatic) phenomenon is called the all-or-none law.

The speed of the impulse down the axon is affected by two factors. First, the larger the diameter of the axons, the more rapidly the impulse is transmitted. Second, many axons are covered with an insulating material called myelin. In myelinated axons, neural impulses “jump” from one break in the myelin sheath—called a node of Ranvier—to another break, resulting in conduction speeds of up to 270 miles per hour. This node-to-node jumping, called saltatory conduction, is much faster than conduction in unmyelinated axons, which produces speeds of only 2 to 22 miles per hour.

Synaptic Transmission

Because a small gap separates one neuron from another, the traveling electrical charge down the axon cannot affect the next neuron electrically: The “wire” is cut. What allows the gap to be bridged is a chemical process that can be described as a sequence that begins with presynaptic events (what occurs in the sending neuron) and ends with postsynaptic events (what occurs in the receiving neuron).

Presynaptically, when the action potential reaches the terminal end bulb, it opens ion channels for calcium ions that then enter the axon. Calcium activates tiny bubbles called vesicles, which contain chemicals called neurotransmitters. The neurotransmitters are chemicals synthesized in the somas of sending neurons that will cause changes in receiving neurons. The activated vesicles will then excrete neurotransmitters into the synaptic cleft. These chemicals will diffuse across the cleft to the postsynaptic neuron. The total process takes approximately two milliseconds.

Postsynaptically, neurotransmitters attach to places on the receiving neuron called receptors. Different receptors are specialized to pick up different kinds of neurotransmitters. Additionally, most of the many kinds of neurotransmitters will have several different types of receptors with which they can interact. Once the neurotransmitter activates the receptor, it may have an excitatory effect, making the postsynaptic cell more likely to produce an impulse, or an inhibitory effect, making the receiving neuron less likely to generate an action potential. Although most neurotransmitters are predominantly excitatory or inhibitory, the ultimate effect of the neurotransmitter depends on the particular receptor. Furthermore, neurotransmitters can alter the activity of the postsynaptic neuron iontropically, by opening ion gates (a quick but brief process), or metabotropically, by initiating metabolic changes (a slow but long-lasting process). Neurotransmitters that do not bind to receptors are usually reabsorbed into the presynaptic neuron or enzymatically broken down, thereby preventing overactivity of the postsynaptic neuron.

Most neurons are on the receiving end of input from many other neurons. How often a synapse is activated (temporal summation), how many innervating synapses are activated (spatial summation), what neurotramsitters are released, and what receptors are involved all combine to determine whether a neuron will produce an action potential.

Brain, Mind, and Neuron

The synaptic network that links neurons is a dynamic system that is highly responsive to the organism’s experience. The more synapses are stimulated, the more efficient they become in their activity. Furthermore, repeated synaptic stimulation increases the number of synapses and induces dendritic branching. This phenomenon, called long-term potentiation, is the neuronal substrate of learning. Long-term potentiation is one reason that those who frequently engage in intellectually stimulating habits, such as reading, develop denser brains than less intellectually stimulated individuals. In other words, an active mind makes for a better brain.

Bibliography

Barnes, Jim. Essential Biological Psychology. London: SAGE, 2012. Print.

Huguenard, John, David A. McCormick, and Gordon M. Shepherd. Electrophysiology of the Neuron: An Interactive Tutorial/Book and Disk. New York: Oxford UP, 1997. Print.

Kalat, James W. Biological Psychology. 10th ed. Belmont: Wadsworth/Cengage Learning, 2009. Print.

Levitan, Irwin B., and Leonard K. Kaczmarek. The Neuron: Cell and Molecular Biology. 3d ed. New York: Oxford UP, 2002. Print.

Liljefors, Max. Atomized Body: The cultural Life of Stem Cells, Genes, and Neurons. Lund: Nordic Academic, 2012. Print.

McKim, William A. Drugs and Behavior: An Introduction to Behavioral Pharmacology. 6th ed. Upper Saddle River: Prentice, 2007. Print.

Nicholls, John G., A. Robert Martin, Paul A. Fuchs, and Bruce G. Wallace. From Neuron to Brain. Sunderland: Sinauer, 2001. Print.

Strominger, Norman L., Rovert J. Demarest, Lois B. Laemle, and Charles Robert Noback. Noback's Human Nervous System: Structure and Function. 7th ed. New York: Humana, 2012. Print.

What were two major changes within American society and culture that were caused by the Cold War?

During the Cold War, Americans were very afraid of communism.  This caused at least two major impacts on American society and culture. 

One of the major impacts was the rise of McCarthyism and related intolerance.  Because Americans were afraid of communism, they supported politicians and others who wanted to root it out.  Those people were willing to accept it when the leaders fingered alleged communists without any real proof that those people actually were communist.  This was the era of “witch hunts” in which people who were alleged to be communist could face serious repercussions simply because they had been accused of sympathizing with communism.  This atmosphere of intolerance in American society was one of the major impacts of the Cold War.

Relatedly, the Cold War also contributed to the rise of conformism in American society during the 1950s.  People in the US at that time did not want to seem different.  In part, they feared that people would think that they were un-American and possibly communist if they acted in ways that were outside the accepted norms.  The conformity that came about in American society because of this is seen as one of the major characteristics of the 1950s in the United States.