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The immune system provides protection against infection by bacteria antifungal treatment for tinea versicolor purchase 250 mg fulvicin amex, viruses fungus weevil order fulvicin 250mg mastercard, fungi fungus gnats washing up liquid purchase 250mg fulvicin with amex, and parasites antifungal hiv fulvicin 250mg visa. The focus of an immune response is an antigen, defined as any molecule (usually a protein) that elicits an immune reaction. The immune system is remarkable in its ability to recognize an almost unlimited number of potential antigens. The body is full of proteins, and so it is essential that the immune system be able to distinguish between self-antigens and foreign antigens. Occasionally, the ability to make this distinction breaks down, and the body produces an immune reaction to its own antigens, resulting in an autoimmune disease (Table 22. Evolution through change in gene expression Another concept revealed by studies in evo-devo is that many major evolutionary adaptations are not through changes in the types of proteins produced but through changes in the expression of genes that encode proteins that regulate development. This concept is seen in the evolution of blind cavefish discussed in the introduction to the chapter, where a small difference in the expression of two transcription-factor-encoding genes, sonic hedgehog and tiggy-winkle hedgehog, cause the development of the lens to abort and result in eyelessness. The birds differ primarily in the size and shape of their beaks: ground finches have deep and wide beaks, cactus finches have long and pointed beaks, and warbler finches have sharp and thin beaks. These differences are associated with diet, and evolutionary changes in beak shape and size have taken place in the past when climate changes brought about shifts in the abundance of food items. They found differences in the expression of a gene that encodes a protein called calmodulin (CaM); the gene that encodes CaM was more highly expressed in the long and pointed beak of cactus-finch embryos than in the beaks of the other species. CaM takes part in a process called calcium signaling, which is known to affect many aspects of development. When Abzhanov and his coworkers activated calcium signaling in developing chicken embryos, the chickens had longer beaks, like those of the cactus finch. Thus, these researchers were able to reproduce, at least in part, the evolutionary difference that distinguishes cactus finches. The importance of this experiment is that it shows that changes in the expression of a single gene in the course of development can produce significant anatomical differences in adults. In these studies and others, the combined efforts of developmental biologists, geneticists, and evolutionary biologists are sources of important insights into how evolution takes place. Lymphocyte stem cell B cell Plasma cell Antibodies 3 When B cells encounter antigens, they mature into plasma cells, which secrete antibodies that bind to the antigen (humoral immunity). Although it is convenient to think of these classes as separate systems, they interact and influence each other significantly. Humoral immunity Immune function is carried out by specialized blood cells called lymphocytes, which are a type of white blood cell. Humoral immunity centers on the production of antibodies by specialized lymphocytes called B cells (Figure 22. Antibodies are proteins that circulate in the blood and other body fluids, binding to specific antigens and marking them for destruction by phagocytic cells. Antibodies also activate a set of proteins called complement that help to lyse cells and attract macrophages. These lymphocytes are responsible for the second type of immune response, cellular immunity. Proteins, called T-cell receptors, on the surfaces of T cells bind to these antigens and mark the infected cell for destruction. Not all T cells attack cells having foreign antigens; some help regulate immune responses, providing communication among different components of the immune system. Clonal selection How can the immune system recognize an almost unlimited number of foreign antigens Remark- ably, each mature lymphocyte is genetically programmed to attack one and only one specific antigen: each mature B cell produces antibodies against a single antigen, and each T cell is capable of attaching to only one type of foreign antigen. If each lymphocyte is specific for only one type of antigen, how does an immune response develop The theory of clonal selection states that, initially, there is a large pool of millions of different lymphocytes, each capable of binding only one antigen (Figure 22. Only a few lymphocytes in the pool will be specific for this particular foreign antigen.

Diseases

• Arthrogryposis epileptic seizures migrational brain disorder
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• Chromosome 4, monosomy 4q32
• Polycystic ovarian syndrome
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• Fanconi syndrome, renal, with nephrocalcinosis and renal stones
• Hereditary resistance to anti-vitamin K
• Monodactyly tetramelic
• Lysosomal alpha-D-mannosidase deficiency

Genes can be distinguished from other sequences by the presence of characteristic features antifungal nail glue purchase 250mg fulvicin free shipping, such as consensus sequences in the promoter and start codon and stop codons within the same reading frame fungus predator animal prey buy fulvicin 250mg without prescription. After potential "candidate" genes have been identified fungus band buy fulvicin 250 mg, they can be evaluated to determine which is most likely to be the gene of interest antifungal for thrush buy generic fulvicin 250mg on line. The expression pattern of the gene-where and when it is transcribed-can often provide clues about its function. For example, genes for neurological disease would likely be expressed in the brain. Geneticists often look in the coding region of the gene for mutations among people with the disease. More will be said about determining the function of genes in sections that follow and in Chapter 20. Through positional cloning, researchers can identify genes that encode a phenotype without having a detailed understanding of the underlying biochemical nature of the phenotype. A number of important human diseases have been identified through positional cloning. Linkage studies are used to map the locus producing a phenotype of interest to a particular chromosome region. Chromosome walking and jumping are used to progress from molecular makers to clones containing sequences that cover the chromosome region. Candidate genes within the region are then evaluated to determine if they encode the phenotype of interest. Restriction enzyme Clone the circularized molecules are cut by a restriction enzyme, producing smaller fragments, in some of which the beginings and ends of the longer fragments are next to each other. Probe Clone A Probe A probe complementary to the end of one clone can be used to find a distant clone. Cystic fibrosis is an autosomal recessive disorder characterized by chronic lung infections, insufficient production of pancreatic enzymes that are necessary for digestion, and increased salt concentration in sweat (Figure 19. Thus, geneticists were seeking an unknown gene-probably encompassing a few thousand or tens of thousands of base pairs-among the 3. Early studies were limited by the paucity of genetic traits that varied and could be used for gene-mapping studies; but, in the 1980s, advances in molecular biology provided a large number of molecular markers that could be used for linkage analysis (see p. The next step was to carry out further linkage studies with additional markers, to more precisely delineate where in the 1. At this stage, geneticists began isolating clones of sequences from the delineated region. Starting from the molecular markers, they used a combina- Linkage analysis was carried out on families with cystic fibrosis. Four candidate genes Further studies of linkage and expression Additional studies eliminated three of the candidate genes. Chloride ions build up in the cell, leading to the formation of thick mucus and the symptoms of the disease. Swe at gla nd Brain Place Liver nta Adre n Testis al gland Paro tid Kidn gland ey Panc rea Nasa s l poly p Lung Colo n 19. These data provided evidence that the candidate gene is in fact that the gene that causes cystic fibrosis. Restriction Fragment Length Polymorphisms A significant contribution of molecular genetics has been to provide numerous genetic markers that can be used in gene mapping. These differences are inherited and can be used in mapping, similar to the way in which allelic differences are used to map conventional genes. From the father, each child inherits either a Huntingtondisease allele (H) or a normal allele (h); any child inheriting the Huntington-disease allele develops the disease, because it is an autosomal dominant disorder. An examination of sequences within these clones revealed the presence of four genes in the region encompassed by the linked makers (see Figure 19. Additional studies were then carried out to better characterize these candidate genes. Hybridization studies were carried out with the one remaining gene to determine where it was expressed. The gene showed high levels of expression in the pancreas, in the lungs, and in sweat glands (Figure 19. The deletion resulted in the absence of a phenylalanine amino acid from the protein encoded by the candidate gene. Pattern A Pattern B 7 this example assumes that Bob is homozygous for the A pattern and Joe is homozygous for the B pattern.

However fungus gnats boiling water buy fulvicin 250 mg on-line, trends in the sheer frequency with which tobacco appears in movies across years do appear to be discordant with declining smoking rates in the actual population fungus gnats damage order 250 mg fulvicin with visa. Mekemson and others22 found a weak decline in the amount of tobacco use per minute of film between 1991 and 2000 fungus gnats vinegar cheap fulvicin 250mg fast delivery. Thus fungus gnats light purchase 250 mg fulvicin amex, the argument that on-screen smoking reflects social realism does not hold up as a reason for trends in the rate of smoking depiction in movies across the years. These results raise questions about the role of films in amplifying notions of tobacco smoking being widespread. A number of movie content analysis studies observed a pattern of increased depiction 371 Trends in the Amount of Tobacco Depicted in Movies Across Years Examination of changes over the years in the frequency of on-screen depiction of tobacco highlights some discrepancies between movie portrayals of smoking and the social reality of smoking. In a content analysis by Dalton and colleagues32 of the top 25 box-office hits from 1988 to 1997, the rate of tobacco use among 1,400 major characters was 25%. McIntosh and colleagues39 found that the proportion of leading characters who smoked increased from 20% in the 1940s to 31% in the 1950s. The proportion then declined to 18% in the 1960s, 17% in the 1970s, and finally 12% in the 1980s. In these three studies, the proportion of characters who smoked does not appear 10. This time span follows the period during which there is documented evidence of paid tobacco product placement deals occurring in relation to film. Examination of trends in the rate of movie depictions of tobacco in relation to key tobacco-control events suggests these events have not precipitated marked reductions in on-screen tobacco portrayals. Hazan and colleagues28 found that between 1960 and 1990, the prevalence of smoking among major characters with high socioeconomic status was nearly three times as high as among people of similar socioeconomic status in the actual U. Future studies 372 replicating sampling and coding methods over time will be necessary to confirm whether a significant decline has occurred in on-screen smoking among teen characters. Dalton and colleagues32 found that only 3% of tobacco occurrences were adolescents smoking and that the typical smoker in movies was white, male, middle-aged, and of high socioeconomic status-traits possessed by most leading characters. Omidvari and colleagues38 found that among leading American movie characters portrayed in the United States in the 1990s, smoking on-screen was associated with being male and of lower socioeconomic class. The different findings of these studies in relation to the apparent class of on-screen smokers may reflect the different sampling methods used. Dalton and colleagues32 and Dozier and colleagues34 selected movies solely on box-office rating. Omidvari and others38 selected a subset of top box-office movies based on a range of exclusion criteria (table 10. The findings of Dalton and colleagues provide an account of smoking prevalence among prominent movie characters during the 1990s across movies of all genres set in all eras. These researchers focused on this subset of movies on the grounds that they were examining how movies portrayed smoking prevalence in contemporary life. Films set in the present may present smokers as more socially disadvantaged than did films in previous eras. The study by Omidvari and colleagues provides a useful snapshot of how contemporary on-screen smoking depictions compare with smoking prevalence in the general U. However, they do not represent a complete picture in terms of audience reach and impact of on-screen smoking (this was not their aim). As Glantz and Polansky43 argue, there is no evidence that viewers, particularly adolescents, distinguish between portrayals of tobacco Monograph 19. The Role of the Media in historical, contemporary, and futuristic films or between portrayals of tobacco in American and non-American films to which they are exposed. The concern about the types of characters who are predominantly depicted as smokers in movies is that smoking is modeled by characters bearing aspirational traits-such as good looks, maturity, affluence, and power-similar to the sorts of images traditionally promoted in tobacco advertisements. Theories of media influence and persuasion predict that role models bearing such traits are the most influential to audiences. Audience studies have not yet examined whether responses vary with the historical setting of smoking. Evidence is emerging, however, that responses vary with character traits of smoking models.

What are some of the major differences in the ways in which genetic information is organized in the genomes of prokaryotes compared with eukaryotes How do the following genomic features of prokaryotic organisms compare with those of eukaryotic organisms A group of 250 scientists sequenced and analyzed the genomes of 12 species of Drosophila (Drosophila 12 Genomes Consortium fungus gnats cinnamon fulvicin 250 mg online. Data on genome size and number of protein-encoding genes from this study are given in Table 20 fungus gnats worms discount 250 mg fulvicin with amex. How does this result compare with the relation between genome size and number of genes across all eukaryotes A scientist determines the complete genomes and proteomes of a live cell and a muscle cell from the same person fungus gnats sticky traps generic 250mg fulvicin overnight delivery. Would you expect bigger differences in the genomes or proteomes of these two cell types What are some characteristics of ribosomal sequences that make them useful for determining what species are present Some synthetic biologists have proposed creating an entirely new antifungal soap for jock itch generic fulvicin 250 mg without prescription, free-living organism with a minimal genome, the smallest set of genes that allows for replication of the organism in a particular environment. This genome could be used to design and create, from "scratch," novel organisms that might perform specific tasks such as the breakdown of toxic materials in the environment. What, if any, social and ethical concerns might be associated with the construction of an entirely new organism with a minimal genome In spite of its long association with human culture, the origins of domesticated donkeys have been uncertain. What little archeological evidence is available suggests that donkeys were domesticated approximately 5000 years ago-about the same time as the domestication of horses. Domesticated donkeys are clearly related to other asses, which include two subspecies of African wild asses, the Nubian wild ass (E. Which of these asses gave rise to donkeys and where domestication took place have, until recently, been unclear. To study the genetic origin of donkeys, Beja-Pereira and his colleagues obtained tissue from domestic donkeys in 52 countries throughout the Old World and from African wild asses and Asian half asses. All the domestic donkeys clustered within the African wild-ass group, indicating that donkeys evolved from the wild asses rather than from the half asses. Another interesting feature indicated by the analysis was that donkeys appear to have at least two distinct origins from African wild asses, as revealed by the fact that some donkeys cluster with the Somalian wild asses and other donkeys cluster with the Nubian wild asses. This finding suggests that at least two independent domestication events took place. There was also significantly more genetic diversity in the domestic donkeys of North Africa than in the donkeys of other regions of the world. The clear affinity between domestic donkeys and African wild asses, coupled with the finding of greater diversity among North African donkeys, suggests that donkey domestication took place at least twice in Africa. Much evidence indicates that the first farm animals-sheep and goats-were domesticated in the Middle East. Donkeys are the only ungulate known to have been domesticated solely in Africa, highlighting the important role North Africa played in early population expansion and trade throughout the Old World. We begin by briefly considering the structures of mitochondria and chloroplasts, the inheritance of traits encoded by their genes, and the evolutionary origin of these organelles. Mitochondrion and Chloroplast Structure Mitochondria are tubular structures that are from 0. In mitochondria, the inner membrane is highly folded; embedded within it are the enzymes that catalyze electron transport and oxidative phosphorylation. Chloroplasts have a third membrane, called the thylakoid membrane, which is highly folded and stacked to form aggregates called grana. New mitochondria and chloroplasts arise by the division of existing organelles-divisions that take place throughout the cell cycle and are independent of mitosis and meiosis.

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