Genetics and Physiological Ageing

• Genes


  Genetic material that determines the characteristics of living organisms
• Genetic conditions


  • Diseases/conditions directly attributed to abnormality of genes
  • Caused by interaction of genes and environmental factors (genetic predisposition)
• Non-disjunction of chromosomes


  • Failure to separate, leading to abnormal numbers of chromosomes
• Down Syndrome


  • Trisomy 21
  • Sperm or egg can carry the extra chromosome
• Turner's and Klinefelter's Syndrome

  • Non-disjunction or duplication of sex chromosomes
  • 45 chromosome not 46 = Turner's Syndrome (single X chromosome)
  • XXY chromosome = Klinefelter's Syndrome (extra X chromosome)
• Genetically linked diseases


  Caused by differences/mutations in certain genetic sequences
• Genes and Environmental Influence

  • Genetic influences and environment work together to cause a disease
  • Environmental influence, e.g. mother's behaviour during pregnancy, can affect genetic material of foetus
• Agents that interfere with normal foetal development (tetragens)

  • Foetal Alcohol Spectrum Disorder
  • Neural tube defects, e.g. spina bifida
  • Phenylketonuria (accumulation of the amino acid phenylalanine in the brain --> intellectual disability)
• Multifactorial Inheritance


  • Many diseases controlled by a number of genes
  • Influences susceptibility to a disease
  • Interaction of genes and environment
• Multifactorial Inheritance


  • Coronary heart disease
  • Obesity
  • Diabetes mellitus Type 1
  • Cancers, e.g. BRCA gene mutation and breast cancer
  • Metabolic disease
  • Certain mental illness
  • Ageing
• Theories of ageing


  1. Genetically programmed to self-destruct

  2. Environmental factors (wear and tear theory)
• Environmental factors (wear and tear theory)

  1. Damage during cell replication = eventual cell death

  2. Atrophy of cells, e.g. in testes, ovaries, breasts

  3. Binding of connective tissue = stiff joints

  4. Free radical effect on cells

  5. Structural changes to bone = osteoporosis

  6. Atherosclerosis = increased BP, increased risk of stroke and heart disease

  7. Oxygen radicals during aerobic metabolism accumulate = destruction fatty acids, protein, DNA, carbs = kill cells
• Cellular changes characteristic of ageing

  • Atrophy
  • Decreased function
  • Loss of cells
• Effects of cellular changes in ageing


  • Compensatory hypertrophy and hyperplasia of remaining cells
  • Aged cell DNA and RNA, cellular proteins and membranes more likely to be injured = mutations, cancers, decreased immunity
• Interplay of factors in ageing

  • Progressive stiffness/rigidity affecting arteries --> leads to resistance to blood flow (hypoxia)
  • Pulmonary and musculoskeletal systems --> diminishes mobility = muscular atrophy = decreased tone and strength (sarcopenia)
• Physiological characteristics of ageing

  • Decreased immunity to bacterial infection
  • Sperm and egg production decreases/ceases
  • Stomach emptying rate decreases
  • Muscles lose contractility
  • Changes to dermis, and epidermis – fragile and wrinkled skin
  • Height decreases
  • Neck, thighs and arms decrease in girth
  • Pelvis widens
  • Ears and nose elongate
  • Decreased muscle and bone mass and density – more likely to fracture bones
  • Less body water is retained – more likely to dehydrate
• The principles of these processes underpin the exploration we will make of specific conditions throughout the unit
• Understanding these processes allows you to understand why the person experiences what they do, why the disease takes the path it does, why certain medical, surgical and pharmacological interventions are applied, and how the disease changes the health status of a person
• This allows you to understand how and when you as a professional can have an impact through your applied discipline-specific knowledge