Genetic Disorders

4 Key excerpts on "Genetic Disorders"

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  eBook - ePub

  Robbins & Kumar Basic Pathology, E-Book

  • Vinay Kumar, Abul K. Abbas, Jon C. Aster, Andrea T Deyrup(Authors)
  • 2022(Publication Date)
  • Elsevier

    (Publisher)

  With the widespread availability of next-generation sequencing technology for assessing DNA copy number variation at very high resolution genome wide, copy number variants have been linked to a higher risk of developing several disorders, including autism. Cancers often contain somatically acquired structural alterations, including amplifications, deletions, and translocations. The so-called “Philadelphia chromosome”—translocation t(9;22) between the BCR and ABL genes in chronic myeloid leukemia (Chapter 10)—is a classic example. With this brief review of the nature of the changes that contribute to the pathogenesis of human diseases, we can turn our attention to the four major categories of Genetic Disorders: • Mendelian disorders resulting from mutations in single genes. These mutations show high penetrance, meaning that most individuals who inherit the anomaly show phenotypic effects. Mendelian disorders are hereditary and familial and include relatively uncommon conditions, such as storage diseases caused by enzyme defects and other inborn errors of metabolism. • Complex disorders involving multiple genes as well as environmental influences. These are called complex, or multifactorial, diseases. They include some of the most common disorders of mankind, including hypertension, diabetes, and allergic and autoimmune diseases. • Diseases arising from changes in chromosomal number or structure. Several developmental diseases such as Down syndrome are attributable to this type of chromosomal alterations. • Other genetic diseases, which involve single gene mutations but do not follow simple mendelian rules of inheritance. These single-gene disorders with nonclassic inheritance patterns include those resulting from triplet repeat mutations or from mutations in mitochondrial DNA, and those in which the transmission is influenced by an epigenetic phenomenon called genomic imprinting

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  eBook - ePub

  Berman's Pediatric Decision Making E-Book

  • Lalit Bajaj, Simon Hambidge, Ann-Christine Nyquist, Gwendolyn Kerby(Authors)
  • 2011(Publication Date)
  • Mosby

    (Publisher)

  Metabolic and Genetic Disorders Passage contains an image Evaluation for a genetic disease

  Gunter H. Scharer, MD

  Before birth and throughout life, genetic factors can cause or contribute to problems of growth, development, cognition, behavior, and general well-being. Knowledge of Genetic Disorders (single-gene defects), genomic imbalances (copy number variations), and abnormalities in gene regulation and gene interaction (epigenetics) plays an ever bigger role in modern medicine. Based on the correct diagnosis, potential complications can be recognized earlier and treated more effectively, adverse effects of existing and new treatments can be minimized, supportive therapies are optimized, and the prognosis for the individual may be predicted more accurately.

  Although correct numbers vary, it is estimated that between 30% and 50% of all admissions to pediatric hospitals occur because of congenital malformations present at birth, or less obvious genetic causes including the contributions of an underlying genetic disorder to the patient’s clinical presentation. Although our understanding of genetics and genetic disease mechanisms does increase rapidly, it will remain incomplete for the foreseeable future. Therefore, we have to rely not only on the results of an increasing number of diagnostic tools, but on the traditional clinical expertise of a dysmorphologist and the critical observations of the bedside clinician–researcher.

  The more classic genetic diseases (major chromosome abnormalities, Mendelian or single-gene disorders) often have a recognizable pattern of prenatal/postnatal growth retardation (including abnormal head size), motor/cognitive delays, muscular hypotonia/hypertonia, and other unique physical features (dysmorphisms). Recognition of specific patterns of multiple birth defects (congenital anomalies) may aid in the diagnosis of the genetic syndrome; however, the majority of birth defects are caused by “multifactorial” interaction of genes and environmental factors.

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  eBook - ePub

  Mayo Clinic Family Health Book

  The Ultimate Home Medical Reference

  • Mayo Clinic(Author)
  • 2019(Publication Date)
  • Mayo Clinic Press

    (Publisher)

  The genes you inherit from your parents are expressed in a variety of ways, but are perhaps most discernible in your physical characteristics, such as the shape of your ears, your eye color and your body type. Genes can also influence the risk of disease, such as heart disease or type 2 diabetes.

  Gene versions (alleles) can be either dominant or recessive. The effects of a dominant allele take precedence over the effects of a recessive allele. In general, for a recessive allele to express itself, it must be paired with a similar recessive allele.

  Variations in genes (polymorphisms) occur on a regular basis and can influence the way genes are expressed. Rarely does a single allelle control one specific trait. Most of the time, traits are governed by the interplay of a variety of genes.

  Down syndrome occurs when one of the reproductive cells from the parents that combine at fertilization contains extra material from chromosome 21. Individuals with Down syndrome usually have three copies of chromosome 21 (trisomy 21) instead of two copies.

  Genetic Disorders

  Understanding how DNA normally functions can help you understand how genetic information might go awry. The topic of genetics and disease is frequently reported in the news, with many reports speculating on how a particular disease may be related to genetic makeup. Understandably, some of the most frequent questions that people now ask their doctors relate to whether a disease can be inherited.

  Genetic Disorders can stem from an abnormality (mutation) in your DNA that’s significant enough to alter the function of a specific protein or other gene product. This abnormality can involve an entire chromosome or a single gene.

  Chromosome abnormalities

  Chromosome abnormalities typically consist of an extra or a missing chromosome. An example is Down syndrome, a condition caused by the presence of extra genetic material from chromosome 21. Most of the time, an entire extra copy of chromosome 21 is present (trisomy 21). Chromosome anomalies such as trisomy 21 may cause intellectual disability and other birth defects.

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  eBook - ePub

  The Status of the Family in Law and Bioethics

  The Genetic Context

  • Roy Gilbar(Author)
  • 2017(Publication Date)
  • Routledge

    (Publisher)

  3 In many cases the effect of the mutation is so severe that the embryo is unable to survive a full term of pregnancy. In other cases a child may be born with a disability, or may develop it during his or her lifetime. In yet other cases the individual may not suffer from a genetic disorder but may carry one mutative copy (out of the two he or she has) and thus may pose a risk to a future offspring.

  When determining a genetic risk, it is important to know that Genetic Disorders are caused in three different ways. First, patients may develop a disorder due to a fault in a single gene (known as single-gene disorders). Second, patients may suffer from a genetic disease because of faults in several genes (known as polygenic disorders ); and finally, they may be disposed to a disease owing to a combination of genetic and environmental factors, such as smoking and diet (known as multifactorial disorders). However, a patient who has a mutation for a genetic disorder is not necessarily affected by it. The proportion of people with the mutation who will be affected is called the 'penetrance' of the condition. A condition has complete penetrance if clinical symptoms are present in all individuals who have the disease-causing mutation. Having reduced or incomplete penetrance is when clinical symptoms are not always present in individuals who have the disease-causing mutation.

  2.1.1.1 Single—gene disorders.

  As noted above, each individual inherits two sets of genes, one from each parent. So with any particular gene an individual may inherit two mutative copies, two healthy copies, or one mutative copy and one healthy copy. Those who receive two healthy copies from their parents will not suffer from the particular disorder. If the individual receives two defective copies of the gene he or she will develop the disorder. However, whether an individual with one faulty copy develops the disorder depends on the mode of inheritance of that particular disorder. In single gene disorders there are three common types of inheritance patterns: dominant, recessive, and X-linked.

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