Lecture Notes: Solving Pedigree Charts Quickly

Introduction

• Speaker: Anatomy Guru
• Audience: Medical students preparing for entrance exams and OSPI in India
• Goal: Learn to solve pedigree charts in under 30 seconds

Key Steps in Solving Pedigree Charts

Step 1: Identify Inheritance Pattern

• Dominant vs Recessive:
  • Dominant: No skipping of generations; continuous sequence (all generations affected)
  • Recessive: Skipping of generations; some generations not affected

Step 2: Differentiate Autosomal vs Sex-linked Inheritance

• Man to Man Transmission:
  • Autosomal Inheritance: Both males and females affected; father can pass trait to son
  • Y-linked Inheritance: Only males are affected, no generation skipping

Step 3: Identify Mitochondrial Inheritance

• Maternally Inherited:
  • Mother passes trait to all children (sons and daughters)
  • Father does not pass trait

Practice with Pedigree Chart Examples

1. Autosomal Dominant Inheritance:

   • Every generation affected, male to male transmission seen

2. X-Linked Dominant Inheritance:

   • Father passes trait to all daughters but not sons

3. Mitochondrial Inheritance:

   • Mother passes trait to all children; father passes to none

4. Autosomal Recessive Inheritance:

   • Skipping of generations, male to male transmission present
   • Males and females equally affected

5. X-Linked Recessive Inheritance:

   • Skipping of generations, no male to male transmission
   • Males more affected than females

Conclusion

• Tips:
  • Use gender effectiveness to differentiate X-linked from autosomal recessive.
  • If males are more affected, likely X-linked recessive.
  • Equal affection: Autosomal recessive.
• Practice charts to quickly identify patterns.

Closing Remarks

• Speaker: Dr. Santh, the Anatomy Guru
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