This Medicoapps Masterclass discusses about Pedigree Chart Analysis. Various Topics Discussed are given Below 1. What are the Various symbols used in Pedigree Chart Analysis ? 2. Classification of Various Types of Inheritance 3. Pedigree Chart Analysis of Autosomal Dominant Inheritance Pattern 4. Pedigree Chart Analysis of Autosomal Recessive Inheritance Pattern 5. Pedigree Chart Analysis of X Linked Dominant Inheritance Pattern 6. Pedigree Chart Analysis of X Linked Recessive Inheritance Pattern 7. Pedigree Chart Analysis of Y Linked Inheritance Pattern 8. Pedigree Chart Analysis of Mitochondrial Inheritance Pattern

1. Pedigree Charts & Analysis

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Pedigree Analysis- Symbols
Normal Male Affected Male Unknown Sex
Normal Female Affected Female
Heterozygous Male
Heterozygous Female
Female Carrier of
X Linked Trait
Deceased Male
Deceased Female
Married
Divorced
Consanguineous
Marriage
Monozygotic
Twins
Dizygotic
Twins

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Types of Inheritance
Autosomal Mitochondrial Sex Linked
Dominant Recessive
X Linked Y Linked
Recessive Dominant

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Basic Concepts
Genotype – GENETIC Make up
Phenotype – Observable Traits
XX
Xx
xx
Allele - Alternative Form of a Gene [One from Each Parent ]
Recessive Trait Dominant Trait
Phenotype
Expression
Phenotype
Expression
Phenotype
Not Expressed
Phenotype
Not Expressed
X x
Homozygous
Heterozygous
XX xx Xx

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Autosomal Dominant Inheritance
One Allele Enough to Manifest (Heterozygous)
Usually one parent affected [Exception – New Mutation ]
Vertical Transmission seen
Skipping of Generation in case of Incomplete penetrance
Autosomal Inheritance (Dominant or Recessive)
Male = Female

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Autosomal Recessive Inheritance
Both Allele Required to Manifest (Homozygous)
Male = Female
Consanguineous marriage common
Horizontal Transmission seen
Pseudo-Dominance
Case of Autosomal Recessive when a Homozygous marries a heterozygous

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X Linked Dominant
Affected Males Transmit to 100% Female (Because Females Receive it from Father)
Male to Male Transmission Never Seen (Because Male Receives it from Mother)
Resembles Autosomal Dominant Pattern of Inheritance

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X Linked Recessive
Males Usually affected and Females usually carriers
Affected Males → Carrier Females
Knight Move (Diagonal ) Pattern of Inheritance
Affected Female only when affected Male marries a carrier female [50% Chance Only]
Carrier Females → Affected Males

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Y Linked Inheritance
Affected males transmits to all males
Also called holandric inheritance [Only Affects males]
DAZ ( Deleted in Azoospermia)
AZF ( Azoospermic Facotr Gene) Mutation causes Azoospermia or Oligospermia
SRY (Sex Reversal Y) codes – Testis Determining Factors (Mutation causes Sex Reversal)

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Mitochondrial Inheritance
Females transmit the Disease to all her Offsprings
Mutant Allele present in mitochondrial DNA
Also Called CYTOPLASMIC INHERTANCE or Matrilineal Inheritance
Autosomal Dominant (65%) > Autosomal Recessive (25%) > X Linked Recessive (5%)

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Analyzing Pedigree Charts in Exam
Autosomal Dominant
Autosomal Recessive
X Linked Dominant
X Linked Recessive
Y Linked
Mitochondrial Inheritance
Affected Father Transmits to all Sons
All Children affected of affected Mother
Affected Male Transmits to 100% of Females
Knight Move / Diagonal Pattern of Inheritance
Male = Female + Vertical Transmission
Male = Female + Horizontal Transmission

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Brain Teaser
Which Type of Inheritance is Shown in the Pedigree Chart