Here's a fact that surprises most NEET aspirants: Genetics + Molecular Inheritance combined are ONE of the four "NEET Biology Core" topics.

After analyzing 26 years of NEET papers (2000–2025), we found:

121 questions dedicated to Genetics
109 questions dedicated to Molecular Basis of Inheritance
Total: 230+ questions from just these two chapters
Appears in 23 out of 26 years – virtually guaranteed
Represents ~8% of the entire NEET paper

Yet most students:

Treat Genetics and Molecular Inheritance as separate, unrelated chapters
Memorise Mendelian ratios without understanding why they work
Skip DNA replication mechanisms and molecular genetics details
Get confused between similar terms (genotype, phenotype, dominance, etc.)

This post is your complete roadmap: how Genetics and Molecular Inheritance are tested, how they connect, which concepts repeat, and how to master both in 21 days.

1. Why Genetics & Molecular Inheritance Matter

The Numbers:

Metric	Genetics	Molecular Inheritance	Combined
Questions (2000–2025)	121	109	230+
Years Appeared	23/26	23/26	Almost all years
% of Biology	~4.2%	~3.8%	~8%
% of NEET	~2.1%	~1.9%	~4%

Combined Importance:

If Genetics + Molecular Inheritance cover ~4% of NEET, that's roughly 29 questions out of 180 Biology marks, or ~16 marks per 100.

A student weak in these two chapters loses 10–15% of Biology marks automatically.

2. Genetics: The Inheritance of Traits

From 121 questions, the topics are:

2.1 Mendelian Genetics (~40–50 questions)

What's tested:

Concept of genes, traits, alleles, dominant vs. recessive
Monohybrid cross: Aa × Aa → 1:2:1 (genotype) or 3:1 (phenotype)
Dihybrid cross: AaBb × AaBb → 9:3:3:1 ratio (phenotypic)
Test cross: Cross with homozygous recessive to determine genotype
Backcross: Cross with one parent
Incomplete dominance & codominance (deviation from 3:1 ratio)

Why it matters:

~6–7 questions per paper directly from Mendelian crosses
Tests both memorisation (ratios) and understanding (why these ratios?)

Common Question Types:

Type A: "Cross two heterozygous tall pea plants (Aa). What percentage of offspring are homozygous?"

→ Aa × Aa → AA (25%), Aa (50%), aa (25%)

→ Homozygous = AA + aa = 50%

Type C: "A red flower plant crossed with white flower gives all pink flowers. What is the inheritance pattern?"

→ Incomplete dominance (neither allele dominant; heterozygote shows intermediate phenotype)

2.2 Linkage & Genetic Recombination (~20–25 questions)

What's tested:

Linked genes: Located on same chromosome, tend to inherit together
Crossing over (recombination): Exchange of DNA between homologous chromosomes
Recombination frequency: % of recombinant offspring = (# recombinant / total) × 100
Map distance: 1 map unit (m.u.) = 1% recombination frequency

Common Question Types:

Type A: "Two genes A and B show 20% recombination frequency. What is the map distance?"

→ 20% recombination = 20 map units (centiMorgans)

2.3 Sex-Linked Inheritance (~15–20 questions)

What's tested:

X-linked genes: Located on X chromosome
Y-linked genes: Located on Y chromosome (only in males)
Carrier females: Heterozygous females carry recessive allele but show dominant phenotype
X-linked recessive traits (colorblindness, hemophilia): Rare in females, common in males

2.4 Chromosomal Aberrations (~10–15 questions)

What's tested:

Aneuploidy: Abnormal number of chromosomes (Monosomy, Trisomy)
Down syndrome (Trisomy 21), Turner syndrome (XO), Klinefelter syndrome (XXY)
Euploidy: Change in whole set of chromosomes (Triploidy, Tetraploidy)

Common Syndromes Tested:

Syndrome	Genotype	Symptoms
Down Syndrome	Trisomy 21 (2n+1)	Intellectual disability, characteristic facial features
Turner Syndrome	XO	Sterile females, short stature
Klinefelter Syndrome	XXY	Sterile males, feminine body traits
Jacob Syndrome	XYY	Tall males

3. Molecular Basis of Inheritance: How Genes Work

From 109 questions, the topics are:

3.1 DNA Structure & Replication (~25–30 questions)

What's tested:

DNA structure: Double helix, Watson-Crick model, base pairing (A-T, G-C)
DNA composition: Deoxyribose sugar, phosphate, nitrogenous bases
Chargaff's rules: %A = %T, %G = %C
Semi-conservative replication: Each strand serves as template
DNA replication mechanism: Helicase, DNA polymerase (5' to 3'), Okazaki fragments, DNA ligase

Common Question Types:

Type A: "DNA replication is semi-conservative. Explain using Meselson-Stahl experiment."

→ Each new DNA molecule has one old strand and one new strand

Type B: "Why is the lagging strand synthesized in short fragments (Okazaki fragments)?"

→ DNA polymerase can only add nucleotides in 5' to 3' direction

3.2 Gene Expression: Transcription & Translation (~30–40 questions)

Transcription: DNA → mRNA (in nucleus)

Promoter region: Where RNA polymerase binds
mRNA processing: 5' capping, 3' polyadenylation, splicing
Three types of RNA: mRNA, tRNA, rRNA

Translation: mRNA → Protein (in ribosome)

Genetic code: Triplet codon, 64 codons (61 sense + 3 stop)
tRNA: Anticodon pairs with codon
Ribosome: Site of protein synthesis (A, P, E sites)

3.3 Genetic Code & Mutations (~20–25 questions)

Genetic code properties: Universal, Triplet, Degenerate, Unambiguous

Types of mutations:

Point mutations: Change one base (missense, nonsense, silent)
Frameshift mutations: Insert/delete bases (cause shift in reading frame)
Chromosomal aberrations: Deletion, duplication, inversion, translocation

4. The Connection Between Genetics & Molecular Inheritance

Students often see these as separate, but they are interconnected:

Genetics (Inheritance) ← Based on → Molecular Inheritance (DNA/Gene mechanism)

Example Chain:

Molecular: DNA codes for proteins that determine phenotype
Genetics: Dominant alleles produce functional protein; recessive alleles may produce non-functional protein
Inheritance: In a 3:1 cross, 3 parts have functional protein (dominant), 1 part has non-functional (recessive)

5. Most Common Genetics & Molecular Genetics Mistakes

Mistake 1: Confusing Genotype & Phenotype

Wrong: "The genotype of a flower is purple."

Reality: Phenotype is purple. Genotype is the genetic code (AA, Aa, or aa).

Mistake 2: Misunderstanding Dominance

Wrong: "Dominant alleles are always more common in the population."

Reality: Dominance is about expression, not frequency.

Mistake 3: Forgetting the "1:2:1" vs. "3:1" Distinction

Ratio	When	Meaning
1:2:1	Genotypic ratio	1 homozygous dominant : 2 heterozygous : 1 homozygous recessive
3:1	Phenotypic ratio	3 dominant phenotype : 1 recessive phenotype

Mistake 4: Wrong Direction in DNA Replication

Wrong: "DNA polymerase adds nucleotides from 3' to 5' direction."

Reality: DNA polymerase synthesizes 5' to 3'.

Mistake 5: Confusing Codons & Anticodons

Feature	Codon	Anticodon
Location	mRNA	tRNA
Reading direction	5' to 3'	3' to 5' (antiparallel)

6. 21-Day Genetics & Molecular Inheritance Mastery Plan

Week	Focus	Daily Work	Target
Week 1	Mendelian Genetics & Linkage	NCERT read + crossing problems	Solve 50+ crossing problems
Week 2	DNA Structure, Replication, Transcription	Deep-dive into mechanisms	Understand replication, transcription
Week 3	Translation, Genetic Code, Mutations	Learn codon table, mutation types + PYQ	Solve 40+ coding questions

Daily Schedule (2–2.5 hours):

Concept read + mechanism diagrams (45 min)
Problem-solving: 15–20 questions (50 min)
Error analysis & revision (15 min)

7. Critical Formulas & Rules

Concept	Formula / Rule
Monohybrid Ratio	3:1 (phenotypic), 1:2:1 (genotypic)
Dihybrid Ratio	9:3:3:1 (phenotypic)
Test Cross	Aa × aa → 1:1 ratio
Recombination Frequency	(# recombinant / total) × 100 = % RF
Map Distance	1 map unit = 1% recombination
Chargaff's Rule	%A = %T, %G = %C
Genetic Code	64 codons (61 sense, 3 stop, 1 start)

8. Call to Action

Ready to Master Genetics & Molecular Inheritance?

✅ Download the "Genetics Cross Problem Solver"
✅ Get the "DNA Replication & Gene Expression Concept Map"
✅ Access the "Genetic Code Codon Table"
✅ Unlock All Genetics & Molecular Inheritance PYQs (2000–2025)
✅ Join the Genetics Study Group

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