Chapter 1: Introduction

Genetics: A Key Discipline of Modern Medicine In some way, each person is like all others In some way like a few In some way unique, like no other. (Origin unknown) All humans are equal, and yet so diverse. We share the same genetic information, with the exception of minute differences, yet we differ in […]

Chapter 2: Molecular Basis of Human Genetics

Introduction What distinguishes the human from other mammalian species? It is not the nucleotides within our DNA sequence, the packaging of DNA into chromosomes, the mechanism of DNA replication, or the translation of genetic information into protein. These components of heredity are similar in all species, from human beings to chimpanzees, to axolotls to Mongolian […]

Chapter 3: Mutations and Genetic Variability

Mutation or Polymorphism? Genetic changes are frequent. New alleles arise at an estimated rate of approximately 70 per diploid human genome per generation. Most of these genetic changes are functionally irrelevant, but some may have minor effects on the phenotype or, occasionally, may be of such serious consequence that the conception will result in a […]

Chapter 4: Pathomechanisms of Genetic Diseases

From Genotype to Phenotype It is unlikely that a patient will seek medical advice by saying, “Good morning, doctor. I have a problem with my compound heterozygosity. On one allele of my CFTR gene is a classical F508del mutation, on the other the 5T-intron variant—this worries me. Can you please help me?” Medical practice deals […]

Chapter 5: Modes of Inheritance

Mendelian Laws of Inheritance Gregor Mendel described the basic tenets of inheritance through his studies of peas in the 19th century. Although chromosomes and genes were yet to be discovered, Mendel’s Laws of Heredity are now applied to human traits and disease, many of which follow mendelian inheritance. The Law of Segregation: The two copies […]

Chapter 6: Twin Pregnancies

Introduction Multiple gestations are rare but now occur at a greater frequency than in the past due to the effects of infertility treatment. While previously a frequency of 1 out of 85 was observed, today 1 in 40 births worldwide involves twins. Twinning associated with infertility treatment is called dizygotic. In the absence of ovulation […]

Chapter 7: Cancer Genetics

Introduction Cancer is second only to cardiovascular disease as the most frequent cause of death in Western, industrialized nations. The “cost” of cancer for the individual, the family, and the nation is substantial and spans many elements, such as direct health care costs, loss of productivity, and costs associated with treatment, research, and development. Most […]

Chapter 8: Aging and Genetics

Introduction In a literal sense, a person begins to age the moment he or she is born; however, true aging at the cellular level doesn’t commence until early adulthood. The pathophysiology of aging is complex; it is characterized in each cell by a limited number of mitoses and is largely associated with the accumulation of […]

Chapter 9: Pharmacogenetics

Introduction For hundreds of years it has been known that medications can have different effects on different people. It has also been known that close relatives often have similar reactions. Adverse drug reactions are among the 10 most frequent causes of death. These include dose-dependent, dose-independent, and dose-over-time-dependent (cumulative) effects, as well as withdrawal, paradoxical […]

Chapter 10: Human Genetics as a Medical Specialty

Introduction Human genetics has four important functions in medicine: Diagnosis of genetic disorders through a detailed personal and family history, physical examination, and diagnostic laboratory evaluation Anticipatory guidance and management regarding interdisciplinary care for individuals with genetic conditions Genetic counseling regarding prognosis, recurrence risk, and availability of patient advocacy associations Clinical and laboratory-based research to […]