Ebook Genetics - A conceptual approad (6/E): Part 2
➤ Gửi thông báo lỗi ⚠️ Báo cáo tài liệu vi phạmNội dung chi tiết: Ebook Genetics - A conceptual approad (6/E): Part 2
Ebook Genetics - A conceptual approad (6/E): Part 2
CHAPTER15The Genetic Code and TranslationThe spleen, an organ found in the lipper abdomen, plays an important role in defense against infection. Isola Ebook Genetics - A conceptual approad (6/E): Part 2ated congenital asplenia is an autosomal dominant condition in which children are born without a spleen.[Sebastian Kaulitzki'Shutterstock.]A Child Without a SpleenThe spleen is an often underappreciated organ. Brownish in color and weighing about a third of a pound, it sits in the left upper part of Ebook Genetics - A conceptual approad (6/E): Part 2 your abdomen, storing blood and filtering out bacteria and old blood cells. The spleen is underappreciated because it’s widely believed that you canEbook Genetics - A conceptual approad (6/E): Part 2
live without a spleen. Indeed, many people who lose their spleen to automobile accidents and other trauma do survive, although they are at increased rCHAPTER15The Genetic Code and TranslationThe spleen, an organ found in the lipper abdomen, plays an important role in defense against infection. Isola Ebook Genetics - A conceptual approad (6/E): Part 2susceptible to life-threatening bacterial infections, and many die in childhood. This rare disorder, known as isolated congenital asplenia (ICA), is inherited as an autosomal dominant trait.Except for the absence of a spleen, children with ICA are unaffected. But their immune function is severely co Ebook Genetics - A conceptual approad (6/E): Part 2mpromised. When infected with bacteria that the immune system normally eliminates, these children develop raginginfections that quickly spread throughEbook Genetics - A conceptual approad (6/E): Part 2
out the body. Even when treated with modern antibiotics, they often die.In 2013, an international team led by scientists from Rockefeller University dCHAPTER15The Genetic Code and TranslationThe spleen, an organ found in the lipper abdomen, plays an important role in defense against infection. Isola Ebook Genetics - A conceptual approad (6/E): Part 2DNA sequences with those of 508 individuals with normal spleens. Statistical analysis pointed to differences in one particular gene that was associated with 1CA, a gene encoding ribosomal protein SA (RPSA). rhe RPSA protein is one of the 33 proteins that make up the small subunit of the ribosome, th Ebook Genetics - A conceptual approad (6/E): Part 2e organelle responsible for protein synthesis. How a defect in the RPSA gene results in the absence of a spleen is not known. Diseases such as ĨGA, whEbook Genetics - A conceptual approad (6/E): Part 2
ich result from defective ribosomes, arc referred to as ribosomopathies.Many, but not all, individuals with 1CA have mutations in RPSA, indicating thaCHAPTER15The Genetic Code and TranslationThe spleen, an organ found in the lipper abdomen, plays an important role in defense against infection. Isola Ebook Genetics - A conceptual approad (6/E): Part 2d premature stop codons, halting translation before a functional protein could be made; one was a frameshift mutation, a change that alters the way the mRNA sequence is read during translation: others changed the amino acid sequence of the RPSA protein.One interesting but unanswered question is why Ebook Genetics - A conceptual approad (6/E): Part 2a defect in RPSA affects only the spleen. Inherited mutations in RPSA occur in every cell of the body, and protein synthesis—carried out by ribosomes—Ebook Genetics - A conceptual approad (6/E): Part 2
is essential for numerous life processes, yet these mutations affect only the development of the spleen. Why aren’t other organs altered? Why aren’t nCHAPTER15The Genetic Code and TranslationThe spleen, an organ found in the lipper abdomen, plays an important role in defense against infection. Isola Ebook Genetics - A conceptual approad (6/E): Part 2y mutations in the KPSA gene affect only the spleen** * ** and not other tissues where ribosomes carry out translation.What are some possible reasons that researchers might be interested in identifying the gene that causes a genetic disease such as 1CA? In other words, what benefits might result fro Ebook Genetics - A conceptual approad (6/E): Part 2m this research?solated congenital asplenia illustrates the extreme importance of translation I the process of protein synthesis, which is the focus oEbook Genetics - A conceptual approad (6/E): Part 2
f this chapter. We J- begin by examining the molecular relation between genotype and phenotype. Next, we study the genetic code—the instructions that CHAPTER15The Genetic Code and TranslationThe spleen, an organ found in the lipper abdomen, plays an important role in defense against infection. Isola Ebook Genetics - A conceptual approad (6/E): Part 2 but we also examine some features of this process in eukaryotic cells. At the end of the chapter, we look at some additional aspects of protein synthesis.15.1 Many Genes Encode ProteinsThe first person to suggest the existence of a relation between genotype and proteins was English physician Archib Ebook Genetics - A conceptual approad (6/E): Part 2ald Garrod. In 1908, Garrod correctly proposed that genes encode enzymes, but unfortunately, his theory made little impression on his contemporaries.Ebook Genetics - A conceptual approad (6/E): Part 2
Not until the 1940s, when George Beadle and Edward Tatum examined the genetic basis of biochemical pathways in the bread mold Neurospora, did the relaCHAPTER15The Genetic Code and TranslationThe spleen, an organ found in the lipper abdomen, plays an important role in defense against infection. Isola Ebook Genetics - A conceptual approad (6/E): Part 2o the one gene, one enzyme hypothesis, the idea that each gene encodes a separate enzyme.THINK-PAIR-SHARE Question 1 ÀÌThe One Gene, One Enzyme HypothesisBeadle and Tatum used Neurosporơ to study the biochemical results of mutations. Neurospora is easy to cultivate in the laboratory, and the main ve Ebook Genetics - A conceptual approad (6/E): Part 2getative part of the fungus is haploid, which allows the effects of otherwise recessive mutations to be easily observed (Figure 15.1).Wild-type NeurosEbook Genetics - A conceptual approad (6/E): Part 2
pora grows on minimal medium, which contains only inorganic salts, nitrogen, a carbon source such as sucrose, and the vitamin biotin. The fungus can sCHAPTER15The Genetic Code and TranslationThe spleen, an organ found in the lipper abdomen, plays an important role in defense against infection. Isola Ebook Genetics - A conceptual approad (6/E): Part 2 the fungus’s ability to synthesize one or more essential biological molecules. These nutritionally deficient mutants, termed auxotrophs (see Chapter 9), cannot grow on minimal medium, but they can grow on medium that contains the substance that they are no longer able to synthesize.Beadle and Tatum Ebook Genetics - A conceptual approad (6/E): Part 2 first irradiated spores of Neurospora to induce mutations (Figure 15.2). Then they placed the spores in different culture tubes with complete mediumEbook Genetics - A conceptual approad (6/E): Part 2
(medium containing all the biological substances needed for growth). These spores grew into fungi and produced spores by mitosis. Next, they transferrCHAPTER15The Genetic Code and TranslationThe spleen, an organ found in the lipper abdomen, plays an important role in defense against infection. Isola Ebook Genetics - A conceptual approad (6/E): Part 2dle and Tatum to identify cultures that possessedmutations.Once they had determined that a particular culture had an auxotrophic mutation, Beadle and Tatum set out to determine the specific effect of the mutation. They transferred spores of each mutant strain from complete medium to a series of tube Ebook Genetics - A conceptual approad (6/E): Part 2s (see Figure 15.2), each of which contained minimal medium plus one of a variety of essential biological molecules, such as an amino acid. If the spoEbook Genetics - A conceptual approad (6/E): Part 2
res in a tube grew, Beadle and Tatum were able to identify the added substance as the biological molecule whose synthesis had been affected by the mutCHAPTER15The Genetic Code and TranslationThe spleen, an organ found in the lipper abdomen, plays an important role in defense against infection. Isola Ebook Genetics - A conceptual approad (6/E): Part 2disrupts the synthesis of arginine.15.1 Beadle and Tatum used the fungus Neurospora, which has a complex life cycle, to work out the relation of genes to proteins.[Narnboori B. Raju, Stanford University.] Ebook Genetics - A conceptual approad (6/E): Part 2CHAPTER15The Genetic Code and TranslationThe spleen, an organ found in the lipper abdomen, plays an important role in defense against infection. IsolaGọi ngay
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