week 17 Embryology and Oncogenesis

• What factors influence ocular disease development in foetal life?


  Genetic and developmental factors, especially during the first trimester, which is vulnerable to pathogens and toxins.
• What structures form from the three germ layers during gastrulation?


  • Ectoderm: Skin, nervous system, retina, lens.
  • Mesoderm: Muscles, blood, connective tissue.
  • Endoderm: Organ linings.
• When do optic vesicles form the optic cup?


  By week 4 of development, creating the retina, iris, and vitreous.
• What conditions can arise from abnormal optic cup closure?


  Coloboma or congenital cataracts
• What visual milestones occur postnatally?


  • 6-8 weeks: Smiling response.
  • 2-4 months: Visual tracking, color vision, binocular fusion.
  • 1-2 years: Achieves 6/6 vision.
• How does meiosis contribute to genetic variation?


  It ensures gametes carry half the DNA, recombining at conception to form unique genetic material.
• What is the role of mitochondrial DNA?


  It is maternally inherited and linked to energy metabolism.
• Give an example of a disease caused by mitochondrial DNA defects.


  Leber’s Hereditary Optic Neuropathy (progressive vision loss).
• What is epigenetic inheritance?


  Altered gene expression due to external factors without changing the DNA sequence, e.g., nutrition affecting disease risk across generations.
• What are the characteristics of autosomal dominance?


  A single faulty gene causes expression. Example: POAG (MYOC gene).
• What are the probabilities in autosomal recessive inheritance?


  25% affected, 50% carriers, 25% unaffected. Example: Stargardt’s disease.
• What is allosomal inheritance?


  Mutations on sex chromosomes (X or Y). Males are more affected due to having only one X chromosome. Example: Color deficiency.
• Define cancer and carcinogenesis.


  • Cancer: Uncontrolled cell division due to mutations.
  • Carcinogenesis: Progressive cell damage leading to tumor formation.
• What are the differences between benign and malignant tumours?


  • Benign: Encapsulated, slow-growing, non-invasive.
  • Malignant: Non-encapsulated, invasive, metastatic, and potentially fatal.
• How are tumors classified?


  By tissue origin, location, and biological behavior. Examples: Carcinoma (epithelium), Sarcoma (connective tissue).
• What is the TNM staging system?


  • T: Tumor size.
  • N: Lymph node involvement.
  • M: Metastasis presence.
• What are common cancer treatments?


  • Surgery: Physical removal.
  • Radiotherapy: Targeted radiation.
  • Chemotherapy: Drugs to kill cancer cells.
  • Immunotherapy: Boosts the immune system.
• Name eye-specific cancers.


  Choroidal melanoma, retinoblastoma, squamous cell carcinoma.
• Benign vs Malignant

  
• Histopathological- according to tissue of origin