(Long Notes) Principles of Inheritance NEET 2025 - UrEducator

BIOLOGIC

INSIGHTS

⚡ NEET 2025 PRINCIPLES OF INHERITANCE ⚡

💎 3 GOLDEN FACTS (NEET 2015-24)

82%

Questions from Mendel's Laws

5x

More pedigree questions than linkage

0

Direct test cross questions since 2019

⚖️ MENDELIAN vs NON-MENDELIAN INHERITANCE

Feature	Mendelian	Non-Mendelian	NEET Frequency
Ratio	3:1 (Monohybrid)	9:3:3:1 (Dihybrid)	3 Q/yr
Dominance	Complete	Incomplete/Codominance	2 Q/yr
Examples	Pea plant traits	ABO blood groups	1 Q/2yr

🧬 Mendel's Laws (1865 Experiments)

Three Fundamental Laws:

• Law of Dominance: Dominant allele expresses in F1 generation
• Law of Segregation: Alleles separate during gamete formation
• Law of Independent Assortment: Genes for different traits assort independently

🧬 Linkage & Crossing Over

Key Concepts:

• Genes < 50 map units apart show linkage
• Crossing over frequency = Map distance
• Complete vs incomplete linkage

Drosophila Example:
Body color (b+) and wing size (vg+) genes show 17.1% recombination

NEET Trick:
"Linked genes disobey Mendel's Law of Independent Assortment"

🎯 PYQ Highlights:

NEET 2021: In monohybrid cross, the phenotypic ratio in F2 generation is? Answer: 3:1

NEET 2019: Which law is violated when genes are linked? Answer: Independent Assortment

🧠 DIHYBRID CROSS MNEMONIC

"Round Yellow Wrinkled Green - 9:3:3:1"

9 Round Yellow : 3 Round Green : 3 Wrinkled Yellow : 1 Wrinkled Green

NEET Hack: Remember "RY-WG" for Round Yellow and Wrinkled Green phenotypes

🧬 Beyond Mendel: Inheritance Patterns

Key Variations:

• Incomplete Dominance: Blending phenotype (e.g., Snapdragon flowers)
• Codominance: Both alleles expressed (e.g., AB blood group)
• Multiple Alleles: More than two alleles (e.g., ABO blood system)
• Polygenic Inheritance: Many genes control one trait (e.g., skin color)

Pleiotropy Example:

Phenylketonuria (PKU): Single gene affects:

• Mental development
• Skin pigmentation
• Hair color

NEET Focus: Marfan syndrome (FBN1 gene affects skeleton, eyes, cardiovascular system)

🎯 PYQ Highlights:

NEET 2022: ABO blood groups show which inheritance pattern? Answer: Multiple Alleles + Codominance

NEET 2020: F1 generation in incomplete dominance shows? Answer: Intermediate phenotype

📊 Pedigree Analysis Masterclass

Pattern Recognition:

• Autosomal Dominant: Affects every generation, both sexes equally
• Autosomal Recessive: Skips generations, more common in consanguinity
• X-linked Recessive: More males affected, no male-to-male transmission
• X-linked Dominant: Affected males pass to all daughters

Sex Determination Systems:

• Humans: XX/XY system (SRY gene on Y chromosome)
• Birds: ZZ/ZW system (female heterogametic)
• Honeybee: Haplodiploidy (females from fertilized eggs, males from unfertilized)

🎯 PYQ Highlights:

NEET 2021: What inheritance pattern shows criss-cross inheritance? Answer: X-linked Recessive

NEET 2018: In a pedigree where only males are affected across generations, what's the likely pattern? Answer: Y-linked

⚠️ Genetic Disorders Breakdown

Must-Know Disorders:

• Autosomal Recessive: Sickle-cell anemia, Cystic fibrosis, PKU
• Autosomal Dominant: Huntington's disease, Marfan syndrome
• X-linked Recessive: Hemophilia, Color blindness, Duchenne MD
• Chromosomal: Down syndrome (Trisomy 21), Turner syndrome (45,X)

Thalassemia (Mendelian Disorder)

Types:

• α-thalassemia: HBA1/HBA2 gene deletion (Chromosome 16)
• β-thalassemia: HBB gene mutation (Chromosome 11)

NEET Pattern: Autosomal recessive → Both parents carriers have 25% affected child

🎯 PYQ Highlights:

NEET 2020: Which disorder results from nondisjunction? Answer: Down syndrome

NEET 2019: Queen Victoria was a carrier for which disorder? Answer: Hemophilia

📈 NEET 2025 Predictions

High Probability Topics:

• Pedigree analysis (especially X-linked patterns)
• ABO blood group inheritance (multiple alleles)
• Chromosomal disorders (Down, Turner, Klinefelter syndromes)

Dark Horse Candidates:

• Genomic imprinting (Prader-Willi/Angelman syndromes)
• Mitochondrial inheritance pattern
• Gene mapping and linkage calculations

🧠 Mnemonics & Quick Recall

"DOMINANT Diseases":
D - Dominant
O - Only one allele needed
M - Manifest in heterozygotes

"X-linked RECESSIVE":
R - Rare in females
E - Expressed in males
C - Carrier mothers

💡 NEET 2025 Master Strategy

• ✅ Practice 50+ pedigree charts (focus on X-linked patterns)
• ✅ Memorize all genetic disorder patterns (make flashcards)
• ✅ Solve all PYQs from 2015-2024 (patterns repeat!)

With these strategies, you'll dominate the Genetics section in NEET 2025! 🧬🚀

🚨 NEET GENETICS ALERT!

Pedigree Analysis asked every year since 2015 - Master it now!

Download Genetics Notes (PDF) PYQs With Solutions More NEET Topics

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