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STUDENT DIGITAL NEWSLETTER ALAGAPPA INSTITUTIONS |
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Mashael Al-Hegelan, MBBS
https://medicine.duke.edu/faculty/mashael-al-hegelan-mbbs
Unmarried pregnant adolescents face social costs antiviral soup buy 10 gr acivir cream with mastercard, which may include rejection by their families symptoms of hiv infection mayo clinic 10 gr acivir cream fast delivery, the end of their education antiviral nclex questions discount 10 gr acivir cream, and the threat of violence hiv infection symptoms pictures trusted 10 gr acivir cream. Girls may resort to unsafe abortion, even where it is illegal and highly dangerous, often involving toxic abortifacients or unsterile procedures, and performed by unskilled practitioners. Even for girls who escape these consequences, early pregnancy may foreclose options for both them and their children, perpetuating poverty and compromising future prospects. For example, do key stakeholders see all adolescent pregnancies as a problem, or only those pregnancies outside marriage A careful assessment of the landscape and engagement of key stakeholders is critical. Young people have rights, and should be partners in planning and programme implementation. Examples include fear-based programmes, information-only programmes, and youth recreation centres. Programmes based on a clear, evidence-based logic model may address the antecedents or associated factors that predispose a young girl to pregnancy. In particular, adolescent participation is not a substitute for political commitment. Mobilize and support partnerships: Partnerships are important to develop consensus about strategies and priorities and facilitate collaboration in advocacy and action. But it is also important not to overestimate what partnerships can achieve, nor to underestimate the time and other resources needed to mobilise and support them. Niruta moved in with the family of Durga, 17, and became pregnant when they were only engaged. At its core are outcomes for adolescent girls: Engagement with learning and decent work; a sense of emotional and physical safety; a positive sense of self and self-efficacy; and the acquisition of life and decision-making skills. The model acknowledges the many influences on adolescents (individual and biological, family, peer, community and national) as they move into their second decade. Implicit in the model is an understanding of the complexity of the risk factors in a given community or national context. Simple solutions to complex problems, while they may be appealing, are rarely effective. It is also critical to understand the contextspecific drivers of adolescent pregnancy. In some places the driver is child marriage; in some, poverty and lack of opportunity seem to offer few options but motherhood; in others girls seek social and adult status. It shows what interventions are geared at whom and at what level can lead to the desired programmatic impact, in this case, a reduction in adolescent pregnancy (see figure 2 right). The interventions in the logic model are aimed toward specific stakeholders who have influence and can play a role in supporting girls to avoid adolescent pregnancy. Crucially, the logic model includes interventions targeted directly at girls, recognizing the importance of asset-building approaches that build their agency, decision-making skills, and other behaviors that put them on a positive path to avoid adolescent pregnancy. At a certain age, the only escape in their mind is to get involved with a boy, and do the same thing. Acknowledging those limitations, there is strong evidence for some programmes that they are effective, and for others that they are promising. To rate inclusion, a programme must have provided evidence either that it directly helped adolescent girls avoid unwanted pregnancy, or that it had an impact on at least one of the known antecedents of adolescent pregnancy such as early school leaving, family poverty or child marriage. Highquality evaluations typically use random assignment and multiple sites including intervention and control sites, and can replicate the findings. Effectiveness does not imply that the intervention alone will reduce adolescent pregnancy; rather, it is considered effective as one of the tools in a multi-level strategy. Nor does adopting a programme rated effective ensure success in all settings; rather, it has a better chance of success than programmes evaluated with less rigorous methods or not at all. Evaluation using pre- and post-testing (also known as baseline and endline data collection) is not as strong as evaluation through random assignment studies, but programmes may still have merit. Such a programme may have had a positive impact or change in a single location: it might well be effective and is included in this review. Such programmes are rated promising when they have been replicated and studied in multiple sites, with similar positive findings. It is important to add that resource constraints or other factors may have prevented careful evaluation. This guidance includes only programmes for which there is some evidence of impact, or at least some indication of a promising approach. This guidance indicates where programmes have had multiple evaluations with different findings, or where impact is reported at one point in time but not subsequently. Many approaches have been repeatedly shown to have no effect either directly or indirectly on adolescent pregnancy, such as short term, fear-based sex education curricula. A programme is effective if it impacts its stated objective; if the objective is associated with adolescent pregnancy reduction, and if evaluation findings reflect the highest quality of evaluation science. Programmes are rated promising when they have been replicated and studied in multiple sites, with similar positive findings. Programmes or approaches are rated potentially promising where there is potential for impact under certain conditions. At the time of their marriage, she was still in school and her husband expressed interest in letting her continue her education. After the birth of her son six-months later, however, Destaye no longer had time for classes. This section reviews what is known about interventions, with comment on the strength of each evaluation. A word of caution is needed: Simply because an intervention has been found to be effective in one or many settings does not imply or guarantee that it will work the same way in your setting. The section focuses on six key groups of stakeholders, from national policy level to individual level, who can foster or derail adolescent development: They are the Six Ps: Policymakers, Programme managers, Providers (including health providers and teachers), Parents, Peers and Partners. Providers (including health providers and teachers), Improved literacy: World Bank data show that independent of income level within country or region of the world, the higher the literacy, the lower the likelihood for an adolescent pregnancy (R. Initiatives include: universal primary and secondary education, investing in school construction, and/or teacher training. Most of these are promising approaches (specific effective interventions are discussed in more detail below). Education prepares girls for jobs and livelihoods, raises their self-esteem and their status in their households and communities, and gives them more say in decisions that affect their lives. Education also reduces the likelihood of child marriage and delays childbearing, leading to healthier eventual birth outcomes. Education of all children increases their capacity to participate socially, economically and politically, but the education of girls leads to special benefits for girls themselves, their families and communities. When girls are educated it reduces the likelihood of child marriage and delays childbearing, leading to healthier eventual birth outcomes. Female education is consistently associated with greater use of family planning, more couple communication about family planning, and lower overall fertility. The authors conclude that while laws are important, they tend rarely to be enforced, and their impact tends to be limited as a result (Child Marriage Fact Sheet 2011). These laws send a strong message that protecting the rights of vulnerable young people, and especially adolescent girls, is a national priority. But without enforcement and given the paucity of evaluation, laws against child marriage are at best promising approaches. While the data are not clear on the extent to which sexual violence contributes to adolescent pregnancy, there is good evidence of such a link among adult women. India, Haiti and the Demographic Republic of the Congo are only three of the countries that have strengthened sexual violence laws recently. These laws have not been evaluated for their effect on pregnancy prevention or any other outcome (Heise 2011). Efficacy undoubtedly resides in enforcement, like child marriage laws; but like these laws they send a message of zero tolerance for sexual and gender violence. The law requires retailers to sell condoms to those over age 12 and allows schools to distribute But without enforcement and given the paucity of evaluation, laws against child marriage are at best promising approaches. This law has yet to be evaluated, so it is not possible to indicate the extent of impact. Colombia has institutionalized the programme throughout the country, and 90 per cent of funding comes from the government. Whether or not it has an impact has yet to be determined but an important step in adolescent pregnancy prevention is to acknowledge that it is a national priority. Still others, such as a programme in the Philippines, incorporate community education and awareness.
Syndromes
For example antiviral pills generic 10 gr acivir cream amex, elevated concentrations of ammonia in the blood cause the symptoms of ammonia intoxication olive leaf antiviral buy 10 gr acivir cream with mastercard, which include tremors hiv infection undetectable viral load acivir cream 10 gr for sale, slurring of speech anti viral remedies discount 10 gr acivir cream mastercard, somnolence (drowsiness), vomiting, cerebral edema, and blurring of vision. Acquired hyperammonemia: Liver disease is a common cause of hyperammonemia in adults and may be due, for example, to viral hepatitis or to hepatotoxins such as alcohol. Cirrhosis of the liver may result in formation of collateral circulation around the liver. As a result, portal blood is shunted directly into the systemic circulation and does not have access to the liver. Therefore, the conversion of ammonia to urea is severely impaired, leading to elevated levels of ammonia. Congenital hyperammonemia: Genetic deficiencies of each of the five enzymes of the urea cycle have been described, with an overall incidence estimated to be 1:25,000 live births. X-linked ornithine transcarbamoylase deficiency is the most common of these disorders, predominantly affecting males, although female carriers may become symptomatic. All of the other urea cycle disorders follow an autosomalrecessive inheritance pattern. In each case, the failure to synthesize urea leads to hyperammonemia during the first weeks following birth. Treatment included restriction of dietary protein in the presence of sufficient calories to prevent catabolism. Administration of compounds that bind covalently to amino acids, producing nitrogen-containing molecules that are excreted in the urine, has improved survival. This condenses with glutamine to form phenylacetylglutamine, which is excreted (Figure 19. Nitrogen leaves the body as urea, ammonia, and other products derived from amino acid metabolism (Figure 19. Free amino acids in the body are produced by hydrolysis of dietary protein by proteases activated from their zymogen form in the stomach and intestine, degradation of tissue proteins, and de novo synthesis. This amino acid pool is consumed in the synthesis of body protein, metabolized for energy, or its members used as precursors for other nitrogen-containing compounds. Free amino acids from digestion are taken up by intestinal cells via sodium-linked secondary active transport. Note that body protein is simultaneously degraded and resynthesized, a process known as protein turnover. The concentration of a cellular protein may be determined by regulation of its synthesis or degradation. Nitrogen cannot be stored, and amino acids in excess of the biosynthetic needs of the cell are quickly degraded. A portion of the free ammonia is excreted in the urine, some of which is used in converting glutamate to glutamine for safe transport, but most is used in the hepatic synthesis of urea, which is quantitatively the most important route for disposing of nitrogen from the body. The two major causes of hyperammonemia (with its neurologic effects) are liver disease and inherited deficiencies of urea cycle enzymes such as X-linked ornithine transcarbamolyase. Transamination reactions always have an amino acid and an -keto acid as substrates. The products of the reaction are also an amino acid (corresponding to the -keto substrate) and an keto acid (corresponding to the amino acid substrate). Three amino acid -keto acid pairs commonly encountered in metabolism are: alanine/pyruvate, aspartate/oxaloacetate, and glutamate/ketoglutarate. In this question, glutamate is deaminated to form ketoglutarate, and oxaloacetate is aminated to form aspartate. Free amino acids are taken into the enterocytes by a proton-linked transport system. Muscle-derived glutamine is metabolized in liver and kidney tissue to ammonia plus a gluconeogenic precursor. The first step in the catabolism of most amino acids is their oxidative deamination. The toxic ammonia generated from the amide nitrogen of amino acids is transported through blood as arginine. Glutamine, produced by the catabolism of branched-chain amino acids in muscle, is deamidated to ammonia plus glutamate. The glutamate is deaminated to ammonia plus - ketoglutarate, which can be used for gluconeogenesis. Healthy, fed individuals are in nitrogen balance, in which nitrogen input equals output. Quantitative plasma amino acid levels revealed a marked elevation of citrulline but not argininosuccinate. Genetic deficiencies of each of the five enzymes of the urea cycle, as well as deficiencies in N-acetyglutamate synthase, have been described. The accumulation of citrulline (but not argininosuccinate) in the plasma of this patient means that the enzyme required for the conversion of citrulline to argininosuccinate (argininosucinate synthetase) is defective, whereas the enzyme that cleaves argininosuccinate (argininosuccinate lyase) is functional. Deficiencies of the enzymes of the urea cycle result in the failure to synthesize urea and lead to hyperammonemia in the first few weeks after birth. Glutamine will also be elevated because it acts as a nontoxic storage and transport form of ammonia. Ornithine will be combined with carbamoyl phosphate by ornithine transcarbamoylase to form citrulline. These pathways converge to form seven intermediate products: oxaloacetate, pyruvate, -ketoglutarate, fumarate, succinyl coenzyme A (CoA), acetyl CoA, and acetoacetate. In contrast, the essential amino acids cannot be synthesized (or produced in sufficient amounts) by the body and, therefore, must be obtained from the diet in order for normal protein synthesis to occur. Genetic defects in the pathways of amino acid metabolism can cause serious disease. Ketogenic amino acids Amino acids whose catabolism yields either acetoacetate or one of its precursors (acetyl CoA or acetoacetyl CoA) are termed ketogenic (see Figure 20. Acetoacetate is one of the ketone bodies, which also include 3-hydroxybutyrate and acetone (see p. Leucine and lysine are the only exclusively ketogenic amino acids found in proteins. Their carbon skeletons are not substrates for gluconeogenesis and, therefore, cannot give rise to the net synthesis of glucose. Aspartate loses its amino group by transamination to form oxaloacetate (see Figure 20. This makes asparagine an essential amino acid for these cells, which, therefore, require asparagine from the blood. Asparaginase, which hydrolyzes asparagine to aspartate, can be administered systemically to treat leukemic patients. Asparaginase lowers the level of asparagine in the plasma, thereby depriving cancer cells of a required nutrient. For example, supplementation with glutamine and arginine has been shown to improve outcomes in patients with trauma, postoperative infections, and immunosuppression. Glutamine: this amino acid is hydrolyzed to glutamate and ammonium by the enzyme glutaminase (see p. Glutamate is converted to -ketoglutarate by transamination or through oxidative deamination by glutamate dehydrogenase (see p. Arginine: this amino acid is hydrolyzed by arginase to produce ornithine (and urea). Alanine: this amino acid loses its amino group by transamination to form pyruvate (Figure 20. Serine: this amino acid can be converted to glycine and N5,N10methylenetetrahydrofolate (Figure 20. Glycine: this amino acid can be converted to serine by the reversible addition of a methylene group from N5,N10-methylenetetrahydrofolic acid (see Figure 20. Deficiency of the transaminase in liver peroxisomes causes overproduction of oxalate, the formation of oxalate stones, and kidney damage (primary oxaluria type 1). Threonine: this amino acid is converted to pyruvate in most organisms but is a minor pathway (at best) in humans. Phenylalanine and tyrosine: Hydroxylation of phenylalanine produces tyrosine (Figure 20. This reaction, catalyzed by tetrahydrobiopterin-requiring phenylalanine hydroxylase, initiates the catabolism of phenylalanine. Thus, the metabolism of phenylalanine and tyrosine merge, leading ultimately to the formation of fumarate and acetoacetate.
In addition garlic antiviral properties buy generic acivir cream 10 gr on line, other treatment measures have usually been instituted hiv infection rate south africa 2011 buy acivir cream 10 gr with amex, making it difficult to draw conclusions about the effectiveness of this treatment antiviral cream for genital herpes discount acivir cream 10 gr overnight delivery. Although there are case reports of success using this modality kleenex anti viral discontinued quality acivir cream 10 gr, a randomized study comparing lactate-buffered peritoneal dialysis to continuous hemofiltration showed that hemofiltration corrected acidosis more quickly and more effectively than peritoneal dialysis. Whether newer bicarbonate-buffered peritoneal dialysis solution is more efficacious remains to be determined. Patients are generally polyuric and polydipsic, but, if volume depletion becomes severe enough, polyuria may not be seen. This hormonal milieu leads to an inability of cells to use glucose, causing them to oxidize fatty acids as fuel, and it results in the production of large amounts of ketoacids. Finally, vomiting may result in a metabolic alkalosis, which would raise the serum bicarbonate toward the normal range. In almost all cases, the acidosis rapidly improves with appropriate management without the use of bicarbonate. However, it is important that these patients be closely monitored with frequent analyses of arterial blood gases and electrolytes. The classic presentation is that of a patient who has been on an alcohol binge, who develops nausea and vomiting, and stops eating. The patient typically presents 24 to 48 hours after the cessation of oral intake and may also complain of abdominal pain and shortness of breath. Patients often have concurrent metabolic alkalosis from vomiting or respiratory alkalosis from liver disease. Finally, electrolyte disorders, including hypokalemia, hypophosphatemia, and hypomagnesemia, are common. Hypovolemia, as demonstrated by hemodynamic compromise, should always be treated first. If insulin is administered precipitously, the rapid uptake of glucose by the cells will cause water to follow because of the fall in extracellular osmolality, potentially resulting in cardiovascular collapse. If the glucose does not decline by 50 to 100 mg/dl/h, the infusion should be increased by 50%. As tissue perfusion improves, -hydroxybutyrate is converted to acetoacetate, and serum ketones paradoxically increase, but then should decrease. When glucose is less than 250 mg/dl, intravenous fluids should be changed to 5% dextrose to avoid hypoglycemia while awaiting resolution of ketogenesis. A subcutaneous insulin dose should be given at least 1 hour before stopping the intravenous insulin infusion to avoid rebound ketosis. Nevertheless, their serum potassium may be normal or high because of a shift from cell stores caused by the profound insulinopenia. When insulin is restored, extracellular potassium is rapidly taken up by cells, and severe hypokalemia may ensue. Therefore, the addition of potassium to the intravenous fluids is recommended at a concentration of 10 to 20 mEq/L as soon as serum potassium falls below 4. Thiamine must be provided before or concurrently with glucose to avoid precipitating Wernicke encephalopathy. Acidosis resolves as insulin increases and counterregulatory hormones are turned off in response to glucose infusion. Ethylene glycol is metabolized by alcohol dehydrogenase into glycolic acid and subsequently into oxalic acid. Diagnosis can be difficult, because ethylene glycol is not detected on routine toxicology assays. A difference greater than about 10 to 15 mOsm/kg suggests the presence of an unmeasured, osmotically active substance, which in the right clinical setting could be a toxin. Some laboratories measure serum osmolality using vapor pressure methodology rather than freezing point depression, and volatile substances such as alcohols may not be detected. As the osmotically active alcohol is metabolized into the various acids, the osmolar gap disappears. Examination of the urine may show calcium oxalate crystals, a finding that can be considered pathognomonic; however, the absence of these crystals does not rule out the ingestion of ethylene glycol. Because fluorescein is added as a colorant to antifreeze, the urine of a patient with antifreeze ingestion may fluoresce under a Wood lamp. Toxicity is usually caused by ingestion of as little as 30 mL, and toxicity has also been reported after inhalation. Blindness may occur because of optic nerve involvement, and pancreatitis may be seen in up to two thirds of patients. The diagnosis of both ethylene glycol and methanol poisoning can Treatment of both ethylene glycol and methanol toxicity is based on the fact that it is the metabolites of these alcohols that are actually harmful and that both substances are metabolized by alcohol dehydrogenase; therefore, blocking the activity of this enzyme will prevent the metabolic acidosis and will allow the alcohol to be excreted by the kidneys or to be removed by dialysis. Because alcohol dehydrogenase has a much higher affinity for ethanol than for either ethylene glycol or methanol, the use of ethanol as a competitive inhibitor is the traditional treatment. However, in some patients with marked ethanol tolerance this rate will need to be doubled. Fomepizole (4-methylpyrazole), a competitive inhibitor of alcohol dehydrogenase, has replaced ethanol as the treatment of choice. An initial loading dose of 15 mg/kg body weight is followed 12 hours later by 10 mg/kg every 12 hours for four doses, then 15 mg/kg every 12 hours for four more doses. Although fomepizole, because of its potency, has begun to call into question the need for dialysis, until more studies are available it is recommended that dialysis be instituted in all patients with suspected ingestions of ethylene glycol or methanol who have end-organ damage (kidney failure or visual impairment) and whose pH is less than 7. Hemodialysis can also help improve the acidosis by providing a source of bicarbonate. It is important to double the rate of any ethanol infusion or to increase the dose of fomepizole while the patient is receiving hemodialysis. For either ingestion, gastric lavage with charcoal should be performed when ingestion has occurred within the preceding 2 to 3 hours. Metabolic acidosis results from the accumulation of both lactic and ketoacids, whereas salicylic acid itself accounts for only a small quantity of the acid load. The patient may also complain of tinnitus when serum concentrations of salicylic acid reach 20 to 45 mg/dl or higher. Both noncardiogenic pulmonary edema and upper gastrointestinal bleeding may occur. In the setting of salicylate overdose, peak serum concentrations are achieved 4 to 6 hours after ingestion. The severity of the ingestion can be predicted by the Done nomogram, which plots the toxic salicylate level at varying points following ingestion. This nomogram cannot be used with chronic ingestions or with the ingestion of enteric-coated aspirin. In addition, because tissue salicylic acid is in equilibrium with the nondissociated compound in the plasma, alkalinization also decreases tissue levels. Concurrent alkalinization of the urine traps salicylate in the tubule, promoting its excretion. Hemodialysis is indicated in all patients with altered mental status, kidney failure that decreases renal excretion, volume overload that prevents the administration of bicarbonate, or salicylate levels greater than 100 mg/dl. This underreported acidosis occurs in patients who usually have underlying infections and are treated with acetaminophen even at therapeutic doses. Glutathione depletion decreases the negative feedback inhibition on -glutamylcysteine synthetase, resulting in an increase in pyroglutamic acid (5-oxoproline). The buffering of protons by bone results in the loss of calcium and negative calcium balance. In addition, chronic acidosis causes protein breakdown, muscle wasting, and negative nitrogen balance. It is rare for maintenance hemodialysis to be initiated solely for the purpose of correcting acidosis. The distal tubule defects can be further divided into those with hypokalemia and those with hyperkalemia. The precise cause of hyporeninemia has not been clearly defined, but the findings that hypertension is frequently present and that the disorder may be partly reversed with chronic furosemide use suggest that renin suppression may be secondary to chronic volume overload. Renin suppression alone should not cause hypoaldosteronism, because hyperkalemia is a potent stimulus of aldosterone secretion and anephric individuals still secrete aldosterone. The acidosis is primarily caused by decreased ammoniagenesis as a result of the associated hyperkalemia induced by the aldosterone deficiency.
Basic concepts of population genetics allow us to understand how and why the prevalence of various genetic diseases differs among populations symptoms for hiv infection buy discount acivir cream 10 gr line. Genotype Frequency Genotype 1-1 1-2 2-2 Total Count 49 42 9 100 Genotype Frequency 0 hiv infection low risk purchase acivir cream 10 gr. The allele frequency measures the proportion of chromosomes that contain a specific allele medicament antiviral zona generic 10 gr acivir cream with mastercard. Each individual with the 1-1 genotype has two copies of allele 1 acute hiv infection fever symptoms 10 gr acivir cream fast delivery, and each heterozygote (1-2 genotype) has one copy of allele 1. A convenient shortcut is to remember that the allele frequencies for all of the alleles of a given locus must add up to 1. Therefore, we can obtain the frequency of allele 2 simply by subtracting the frequency, of allele 1 (0. This relationship, expressed in the Hardy-Weinberg equation, allows one to estimate genotype frequencies if one knows allele frequencies, and Viceversa: the Hardy-Weinberg Equation In this equation: p = frequency of allele 1 (conventionally the most common, normal allele) q = frequency of allele 2 (conventionally a minor, disease-producing p2 = frequency of genotype 1-1 (conventionally homozygous normal) 2pq = frequency of genotype 1-2 (conventionally heterozygous) q2 = frequency of genotype 2-2 (conventionally homozygous affected) In most cases where this equation is used, a simplification is possible. Although the Hardy-Weinberg equation applies equally well autosomal dominant and recessive alleles, genotypes, and diseases, the equation is most frequen used with autosomal recessive conditions. She is aware that she has an autosomal recessive genetic disease that bas required her lifelong adherence to a diet low in natural protein with supplements of tyrosine and restricted amounts of phenylalanine. She asks her genetics professor about the chances that she would marry a man with the disease-producing allele. First, the frequency of carriers for this condition is much higher than the frequency of affected homozygotes, and second, an affected person would be identifiable clinically. If events are nonindependent, multiply the probability of one event by the probability of the second event, assuming that the first has occurred. It is the probability that he will be a carrier (1/50, event 1) multiplied by the probability that he will pass the diseasecausing gene along (1/2, event 2), assuming that he is a carrier. In contrast, in Huntington disease (autosomal dominant), the number of triplet repeats corre-: lates much more strongly with disease severity than does heterozygous or homozygous status. In some cases, a new mutation can be introduced into a population when someone carrying the mutation is one of the early fo~nders of the community, this is referred to as a founder effect. The predominance of a single mutation (allele) in the branched chain dehydrogenase gene in this group suggests a common origin of the mutation. I Natural Selection Natural selection acts upon genetic variation, increasing the frequencies of alleles that promote survival, or fertility (referred to as fitness) and decreasing the frequencies of alleles that reduce fitness. The reduced fitness of most disease-producing alleles helps explain why most genetic diseases are relatively rare. Dominant diseases, in which the disease-causing allele is more readily exposed to the effects of natural selection, tend to have lower allele frequencies than, do recessive diseases, where the allele is typically hidden in heterozygotes. The answer lies in the fact that the falciparum malaria parasite, which has been common in much of Africa, does not survive well in the erythrocytes of sickle cell heterozygotes. These individuals, who have no clinical signs of sickle cell disease, are thus protected against the lethal effects of malaria. Mutation rates and founder effects act along with genetic drift to make certain genetic diseases more common (or rarer) in small, isolated populations than ill the world at large. Gene flow can also cause gene frequencies to change through time: the frequency of sickle cell disease is lower in African Americans in part because of gene flow from other sectors of the u. Consanguinity and Its Health Consequences Consanguinity refers to the mating of individuals who are related to one another (typically, a union is considered to be consanguineous if it occurs between individuals related at the secondcousin level or closer). Statistically, Note Consanguineous matings are more likely to produce offspring affected with recessive diseases because individuals who share common ancestors are more liable to share disease-causing mutations. Dozens of empirical studies have examined the health consequences of consanguinity, particularly first-cousin matings. The frequency of genetic disease increases further in the offspring of closer unions. Chapter Summary Population genetics allows predictions about the prevalence of diseases in populations. Gene (allele) frequency measures the proportion of each allele at a particular locus. Because the couple shares approximately half of their genes, most of the offspring are likely to be affected with some type of genetic disorder. The couple has an increased risk of producing a child with an autosomal dominant the couple has an increased risk of producing a child with an autosomal recessive disease. They have asked why this disease seems to be more common in the African American population than in other U. Consanguinity Genetic drift Increased gene flow in this population Increased mutation rate in this population Natural selection 5. If the incidence of cystic fibrosis is 1/2,500 among a population of Europeans, what is the predicted incidence of heterozygous carriers of a cystic fibrosis mutation in this popula- " tion A man is a known heterozygous carrier of a mutation causing hyperprolinemia, an autosomal recessive condition. Phenotypic expression is variable and ranges from high urinary excretion of proline to neurologic manifestations including seizures: Suppose that 0. If the man mates with somebody from the general population, what is the probability that he and his mate will produce a child who is homozygous for the mutation involved The incidence of Duchenne muscular dystrophy in North America is about 1/3,000 males: On the basis for this figure, what is the gene frequency of this X-linked recessive mutation A man who is a known heterozygous carrier of oculocutaneous albinism marries his halfcousin (they share one common grandparent) as shown in the pedigree below. What proportion of individuals in this population would be expected to be heterozygous carriers of the sickle cell hemoglobin gene The numerator is obtained by counting the number of alleles of each type: the 4 homozygotes with the 1,1 genotype contribute 8 copies of allele 1; the 1,3 heterozygotes contribute another 8 alleles; and the 1,4 heterozygotes contribute 3 alleles. For allele 2, there are two classes of heterozygotes that have a copy of the allele: those with the 2,3 and 2,4 genotypes. The incidence of affected homozygotes permits the estimation of the frequency of the recessive mutation in the population. Consanguinity (choice A) affects Hardy-Weinberg equilibrium by increasing the number of homozygotes in the population above the equilibrium expectation. Genotype frequencies can be estimated from gene frequencies (choice B), but gene frequencies can also be estimated from genotype frequencies (as in choice A). Only one generation of random matingis required to return a population rium (choice D). Thus, their risk of producing a child with an autosomal recessive disease is elevated above that of the general population. In addition, consanguinity itself does not elevate the probability of producing a child with a dominant disease because only one, copy of the disease-causing allele is needed to cause the disease. Empirical studies indicate that the risk of genetic disease in the offspring of first cousin. Consanguinity (choice A) could elevate the incidence of this autosomal recessive disease in a specific family, but it does not account for the elevated incidence of this specific dis-. Although there has been gene flow (choice C) from other populations into the African American population, this would be expected to decrease" rather than increase, the frequency of sickle cell disease because the frequency of this disease is highest in some African populations. There is no evidence that the mutation rate (choice D) is elevated in this population. If the frequency of affected hornozygotes (q2) is 1/40,000, then the allele frequency, q, is 1/200. Three independent events must happen for their child to be homozygous for the mutation. The mate must be a carrier (probability 1/100), the mate must pass along the mutant allele (probability 1/2), and the man must also pass along the mutant allele (probability 1/2). Multiplying the three probabilities to determine the probability of their joint occurrence gives 1/100 x 1/2 x 1/2 = 1/400.
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