Genetics Overview

• Genetics: Study of variation and heredity in living organisms.

  • Cytogenetics: Study of chromosomes.

  • Molecular Genetics: Structure and function of individual genes.

  • Genomics: Study of the genome, its organization, interaction, and functions.

Importance of Genetics

• Human Diseases Classification:

  • Genetically Determined

  • Environmental & Genetically Determined

  • Environmentally Determined

  • Hereditary: Derived from parents, transmitted through germ line.

  • Congenital: Inborn conditions.

  • Examples:

    • Congenital but not genetic: Congenital syphilis.

    • Genetic but not congenital: Huntington disease.

Classification of Genetic Disorders

• Single-Gene Disorders:

  • Caused by mutations in individual genes.

  • Examples: Thalassemia, Sickle-cell anemia, Hemophilia.

• Chromosomal Disorders:

  • Result from excess or deficiency of genes in chromosomes.

  • Examples: Trisomy 21 (Down syndrome), Turner syndrome.

• Multifactorial Disorders:

  • Caused by combination of genetic variations and environmental factors.

  • Examples: Diabetes, Cancer, Schizophrenia.

Specific Chromosomal Disorders

• Trisomy 21 (Down Syndrome):

  • Occurs in 1 in 700 live births.

  • Symptoms: Mental retardation, congenital heart anomalies, etc.

  • Associated with advanced maternal age and extra 21st chromosome.

• Trisomy 18 (Edwards Syndrome) & Trisomy 13 (Patau Syndrome):

  • More severe than Down syndrome; may lead to congenital anomalies at birth.

Syndromic Genetic Disorders

• Klinefelter Syndrome:

  • 1 in 850 live births; extra X chromosome (XXY).

  • Symptoms: Abnormal sexual development, infertility, etc.

• Turner Syndrome:

  • Monosomy X, affecting 1 in 3000 female births.

  • Symptoms: Short stature, sterility, congenital heart defects.

Mendelian Disorders

Autosomal Dominant Disorders

• Patterns of inheritance:

  • 1 in 2 chance of passing the disorder to offspring.

  • Common examples: Huntington disease, Neurofibromatosis.

Autosomal Recessive Disorders

• Disease not apparent in parents; carriers can transmit.

  • Examples: Sickle cell anemia, Albinism.

Sex-Linked Disorders

• X-linked conditions affect mostly males; carriers are typically female.

  • Example: Hemophilia A.

Cancer Overview

• Neoplasia: New growth; includes benign and malignant tumors.

  • 2nd leading cause of death; characterized by rapid growth of cells.

Tumor Classification

• Benign Tumors vs. Malignant Tumors:

  • Characteristics: Growth rate, localization, metastasis, prognosis.

  • Benign: Typical histology, localized, capsulated.

  • Malignant: Anaplastic cells, infiltrative, may metastasize.

Carcinogenesis Mechanisms

• Carcinogenesis phases: Initiation, Promotion, Progression.

  • Involves genetic mutation and influencing factors (carcinogens).

• Key elements: Proto-oncogenes and tumor suppressor genes (e.g., Rb, P53).

Cancer Therapy

• Common treatments include:

  • Surgery, Radiation, Chemotherapy, Immunotherapy.

Risk Factors for Cancer

• Tobacco Use: Causes lung and other cancers.

• Diet: Low fiber, high calories linked to colon cancer.

• Alcohol Use: Increases risk for liver and oral cancers.