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NEET PG previous year questions genetic pedigree analysis X-linked autosomal recessive disease PYQ

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NEET PG MCQ pedigree chart X-linked recessive autosomal dominant previous year questions answers 2022 2023 2024

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https://www.slideshare.net/slideshow/pedigree-problems-neet/…

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I now have all I need. Here is a complete NEET PG question set on Genetic Pedigree Analysis and X-linked / Recessive Disease, drawn from actual PYQs (NEET UG 2009-2023, NEET PG pattern):

🧬 NEET PG - Genetic Pedigree & Recessive Disease - PYQ Set

SECTION A: PEDIGREE ANALYSIS - IDENTIFY MODE OF INHERITANCE

Q1. ⭐ NEET 2015 (Classic PYQ)

In the following human pedigree, filled symbols represent affected individuals. Normal parents in Generation I give rise to affected offspring in Generations II and III. The trait skips some individuals. An affected daughter in Generation II has a normal son in Generation III.

Identify the type of inheritance:

A) Autosomal Recessive
B) X-linked Dominant
C) Autosomal Dominant
D) X-linked Recessive

✅ Answer & Explanation

Answer: A - Autosomal Recessive

Step-by-step reasoning:

Normal parents → affected offspring = Recessive (rules out B and C)
Trait skips generations; not all offspring affected = Recessive confirmed
If X-linked recessive: an affected daughter (X^r X^r) would pass X^r to ALL her sons → all sons should be affected
But the son in Gen III is normal → X-linked ruled out (rules out D)
Therefore: Autosomal Recessive ✔

Key Rule: If an affected mother has a normal son → NOT X-linked recessive

Q2. ⭐ NEET 2009 (Classic PYQ)

Study the pedigree chart. Both parents are normal. They have affected children of both sexes across multiple generations.

What does the pedigree show?

A) Inheritance of a condition like phenylketonuria as an autosomal recessive trait
B) The pedigree chart is wrong as it is not possible
C) Inheritance of a recessive sex-linked disease like haemophilia
D) Inheritance of a sex-linked inborn error of metabolism like phenylketonuria

✅ Answer & Explanation

Answer: A - Autosomal recessive (like PKU)

Reasoning:

Normal parents → diseased offspring in Generations II and III = Recessive
Both sexes are affected equally = Autosomal (not sex-linked)
Phenylketonuria (PKU) is the classic example of autosomal recessive metabolic disease
Option C (haemophilia) is X-linked recessive, affects mostly males
Option D is wrong - PKU is autosomal, NOT sex-linked

Q3. ⭐ NEET 2010 (Classic PYQ)

In a pedigree, an affected father (X^A Y) mates with a normal female. They have a normal daughter. The trait is colour blindness.

Which statement is correct?

A) The trait is autosomal recessive
B) The parents could not have had a normal daughter for this character
C) The trait under study could not be colour blindness
D) The male parent is homozygous dominant

✅ Answer & Explanation

Answer: B

Reasoning:

Colour blindness is X-linked recessive
An affected father (X^cb Y) x carrier/normal mother (X^N X^N or X^N X^cb)
If mother is X^N X^N: daughters get X^N from mom + X^cb from dad = X^N X^cb (carrier, phenotypically normal) ✔
Normal daughters ARE possible - she would be a carrier
But option C says "could not be colour blindness" - this is wrong because colour blindness IS X-linked recessive
The correct answer is B if the pedigree shows the normal daughter should have been affected (context-dependent)

Important: Colour blindness = X-linked recessive → Option C is ruled out as a distractor

SECTION B: RECESSIVE DISEASE IDENTIFICATION (PYQ-Style)

Q4. Which of the following is an Autosomal RECESSIVE disorder? (PYQ Repeat Pattern)

A) Huntington's disease
B) Marfan syndrome
C) Phenylketonuria (PKU)
D) Neurofibromatosis type 1

✅ Answer: C - PKU

Disease	Inheritance
PKU (Phenylketonuria)	Autosomal Recessive ✔
Huntington's disease	Autosomal Dominant
Marfan syndrome	Autosomal Dominant
Neurofibromatosis type 1	Autosomal Dominant

Other AR diseases to remember: Cystic fibrosis, Sickle cell anemia, Thalassemia, Alkaptonuria, Galactosemia, Wilson's disease, Friedreich's ataxia

Q5. Which of the following is an X-linked RECESSIVE disorder? (PYQ Repeat Pattern)

A) Fragile X syndrome
B) Haemophilia A
C) Turner syndrome
D) Treacher Collins syndrome

✅ Answer: B - Haemophilia A

Disease	Inheritance
Haemophilia A (Factor VIII deficiency)	X-linked Recessive ✔
Haemophilia B (Factor IX)	X-linked Recessive
Colour blindness	X-linked Recessive
Duchenne Muscular Dystrophy	X-linked Recessive
Fragile X syndrome	X-linked Dominant (technically)
Turner syndrome	Chromosomal (45,X)
Treacher Collins	Autosomal Dominant

Q6. A 6-year-old boy has progressive muscle weakness. His mother's brother also had the same disease. Pedigree shows only males affected across generations, linked through carrier females. What is the diagnosis?

A) Myotonic dystrophy
B) Duchenne Muscular Dystrophy (DMD)
C) Becker Muscular Dystrophy
D) Emery-Dreifuss syndrome

✅ Answer: B - Duchenne Muscular Dystrophy

Key features of DMD:

X-linked recessive (gene: dystrophin on Xp21)
Onset: 3-5 years
Calf pseudohypertrophy (classic)
Gowers sign (rising from floor using hands)
Maternal uncle affected = classic X-linked pattern
Serum CK markedly elevated
Death usually by 2nd decade (respiratory failure)

Becker MD = same gene, milder, survives to adulthood

Q7. Consanguinity (cousin marriage) increases the risk of which type of disorder? (PYQ Concept)

A) Autosomal Dominant
B) X-linked Dominant
C) Autosomal Recessive
D) Chromosomal aneuploidy

✅ Answer: C - Autosomal Recessive

Reasoning:

Consanguinity (marriage between relatives) increases the probability of both parents carrying the same rare recessive allele inherited from a common ancestor
This dramatically increases the risk of homozygous recessive offspring
Classic example: PKU, cystic fibrosis, thalassemia in certain populations

SECTION C: PEDIGREE REASONING RULES - QUICK REVISION TABLE

Finding in Pedigree	Interpretation
Normal parents → affected child	Recessive
Affected parent → affected child every generation	Dominant
Only males affected, linked through females	X-linked Recessive
Affected mother has all affected sons	X-linked Recessive
Affected mother has normal sons	NOT X-linked recessive (Autosomal Recessive)
Affected father cannot transmit to sons	X-linked (no father-son transmission)
Both sexes equally affected	Autosomal
Maternal uncle affected like nephew	X-linked
Consanguinity in pedigree	Suggests Autosomal Recessive

🎯 High-Yield Diseases to Know for NEET PG

Inheritance	Diseases
Autosomal Recessive	PKU, Cystic Fibrosis, Sickle Cell, Thalassemia, Wilson's, Alkaptonuria, Gaucher, Niemann-Pick
Autosomal Dominant	Huntington's, Marfan, ADPKD, NF1, NF2, Achondroplasia, FAP
X-linked Recessive	Haemophilia A&B, DMD, Becker MD, G6PD deficiency, Colour blindness, Wiskott-Aldrich
X-linked Dominant	Fragile X, Rett syndrome, Vitamin D-resistant rickets
Mitochondrial	MELAS, MERRF, Leber's optic neuropathy (maternal inheritance)

Pro Tip for NEET PG: The most commonly tested pedigree type is Autosomal Recessive - always look for: (1) normal parents with affected child, (2) consanguinity, (3) horizontal pattern (siblings affected, not parents). For X-linked, remember: no father-to-son transmission is the hallmark.

Pedigree chrt ils

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I found the pedigree chart images from Harrison's and Emery's genetics textbooks. Let me fetch them all:

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Here are all the pedigree chart illustrations from medical genetics textbooks:

🧬 Pedigree Chart Illustrations

1. Standard Pedigree Symbols (Emery's Medical Genetics)

(From Emery's Elements of Medical Genetics and Genomics)

Key Symbols to Remember:

Symbol	Meaning
Square (□)	Male
Circle (○)	Female
Diamond (◇)	Unknown sex
Filled/Shaded	Affected individual
Half-filled	Carrier (heterozygote)
Double horizontal line	Consanguineous mating (cousin marriage)
Dotted line	Adoption
"P" with arrow	Proband (index case)
Diagonal slash	Deceased

2. All 4 Inheritance Patterns - Pedigree Charts (Harrison's Internal Medicine 22E)

(From Harrison's Principles of Internal Medicine, 22nd Edition)

How to Identify Each Pattern:

A - Autosomal Dominant:

Every generation affected (vertical transmission)
Affected father can pass to son (male-to-male transmission present)
50% offspring affected
Examples: Huntington's, Marfan, NF1, Achondroplasia

B - Autosomal Recessive:

Normal parents → affected children (horizontal pattern)
Siblings affected, not parents
Both sexes equally affected
Double line (consanguinity) often present
Half-filled circles = carriers
Examples: PKU, Cystic Fibrosis, Thalassemia, Sickle cell

C - X-linked Recessive:

Only males are fully affected (filled squares)
Females are carriers (circle with dot)
NO father-to-son transmission
Affected grandfather → carrier daughter → affected grandson ("knight's move")
Examples: Haemophilia A/B, DMD, Colour blindness, G6PD deficiency

D - Mitochondrial (Matrilineal):

Affected MOTHER passes to ALL children (sons + daughters)
Affected father passes to NONE
All children of an affected mother are affected
Examples: MELAS, MERRF, Leber's optic neuropathy

3. Allele Segregation Ratios (Harrison's)

(Showing genotype distribution across different cross combinations)

Ratio Quick Summary for NEET PG:

Cross	Ratio (Affected : Carrier : Normal)
Aa × aa (AD affected × normal)	50% affected : 50% normal
Aa × Aa (two carriers, AR)	25% AA : 50% Aa : 25% aa (1 in 4 affected)
AA × aa (homozygous × normal)	100% carriers (Aa), none affected

🎯 NEET PG Pedigree - Cheat Sheet

AUTOSOMAL DOMINANT        AUTOSOMAL RECESSIVE
Every generation          Skips generations
Both sexes               Both sexes
Father → son OK          Consanguinity common
50% risk                 25% risk

X-LINKED RECESSIVE        MITOCHONDRIAL
Only males affected      ALL children of mother
Carrier females          affected
NO father → son          Father passes to NONE
Maternal uncle pattern

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