Скачать или смотреть Genes and Genetic Diseases | Chapter 2 - Understanding Pathophysiology (7th Edition)

Chapter 2 of Understanding Pathophysiology (Seventh Edition) by Sue E. Huether, Kathryn L. McCance, and Valentina L. Brashers, with contributions by Lynn B. Jorde, explores the molecular and clinical foundations of heredity, focusing on how genetic material influences health and disease. The chapter begins with DNA structure, explaining nucleotides, complementary base pairing, the Watson-Crick double-helix model, and how DNA encodes proteins through codons and the processes of transcription and translation. It describes the roles of mRNA, tRNA, and rRNA in protein synthesis, highlighting introns, exons, and gene splicing. DNA replication and proofreading by DNA polymerase are examined alongside mutations—silent, missense, nonsense, and frameshift—and their consequences for genetic disorders. Chromosomes are discussed in depth, including diploid vs haploid cells, autosomes, sex chromosomes, and karyotypes, with attention to abnormalities such as polyploidy, aneuploidy, nondisjunction, and chromosomal mosaics. Clinical examples include Down syndrome (trisomy 21), Turner syndrome (45,X), and Klinefelter syndrome (47,XXY), as well as structural alterations like deletions (cri du chat syndrome), duplications, inversions, and Robertsonian translocations. The section on fragile sites introduces fragile X syndrome, the second most common cause of intellectual disability. The chapter then transitions to Mendelian genetics, covering genes, alleles, loci, homozygous vs heterozygous states, genotype vs phenotype, and polymorphism. Patterns of inheritance are explained through autosomal dominant diseases (e.g., Huntington disease, retinoblastoma, neurofibromatosis), autosomal recessive conditions (e.g., cystic fibrosis, PKU, Tay-Sachs), and X-linked inheritance (e.g., Duchenne muscular dystrophy), with detailed discussion of recurrence risk, penetrance, expressivity, delayed onset, and consanguinity. The Lyon hypothesis and X inactivation are outlined to explain dosage compensation, Barr bodies, and X-linked mosaics. The chapter also addresses sex determination via the SRY gene on the Y chromosome, alongside exceptions such as XX males and XY females. Epigenetics and genomic imprinting are explored, showing how DNA methylation and parent-specific imprinting can cause disorders like Beckwith-Wiedemann syndrome, Prader-Willi syndrome, and Angelman syndrome. Finally, the chapter explains linkage analysis, gene mapping, and the Human Genome Project’s role in identifying Mendelian conditions and advancing gene therapy. Multifactorial inheritance is introduced, where traits arise from polygenic influences and environmental interactions, illustrated by examples like pyloric stenosis, cleft lip/palate, neural tube defects, heart disease, diabetes, and hypertension. This chapter provides a comprehensive overview of molecular genetics, chromosomal biology, inheritance patterns, and their pathophysiologic implications, establishing a strong foundation for understanding how genetic variation drives human disease.

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