Genetics (अनुवांशिकी) | Biology Notes (Hindi)
Genetics (अनुवांशिकी) वंशानुक्रम, जीन, गुणसूत्र और आनुवंशिकता की शास्त्रीय व आधुनिक अवधारणाएँ हैं। SSC, RRB व राज्य परीक्षाओं में Mendel के नियम, DNA/RNA, प्रकार की विरासत (Dominant/Recessive, Co-dominance), mutations, genetic disorders और बायोटेक्नोलॉजी के सामान्य प्रश्न अक्सर पूछे जाते हैं। नीचे परीक्षा-अनुकूल सार, तालिकाएँ और 20 MCQs दिए गए हैं।
1. Basic Terms (मूल शब्दावली)
- Gene (जीन): वारिस गुण का एक यूनिट, DNA का विशेष अनुक्रम।
- Allele (एलिल): किसी जीन के वैकल्पिक रूप (उदा. A या a)।
- Genotype: आनुवंशिक संरचना (जीन कॉम्पोजिशन)।
- Phenotype: प्रकट लक्षण/रूप (देखने योग्य)।
- Homozygous / Heterozygous: समान/विभिन्न एलिल्स।
- Chromosome: DNA + proteins में पैक्ड संरचना; मानव में 46 (23 जोड़े)।
2. Mendelian Genetics (मैंडेलियन अनुवांशिकी)
- Gregor Mendel के प्रयोग: Pisum sativum (Garden pea) पर ब्रिज़; Laws of Inheritance।
- Law of Segregation: Alleles segregate during gamete formation (Meiosis)।
- Law of Independent Assortment: अलग-अलग gene pairs स्वतंत्र रूप से assort होते हैं (non-linked genes)।
- Monohybrid cross → 3:1 phenotype ratio (F₂) if one allele dominant.
3. Types of Inheritance (विरासत के प्रकार)
| Type | Pattern | Example |
|---|---|---|
| Complete dominance | Dominant masks recessive | Pea: Tall (T) over short (t) |
| Incomplete dominance | Heterozygote = intermediate phenotype | Snapdragon: Red × White → Pink |
| Co-dominance | Both alleles expressed | AB blood group (A & B both) |
| Sex-linked | Gene on X chromosome | Color blindness, Hemophilia |
| Polygenic | Multiple genes affect trait | Skin color, Height |
4. Chromosomes & DNA (गुणसूत्र व DNA)
- Human somatic cells: 46 chromosomes (23 pairs) — 22 autosomes + 1 pair sex chromosomes (XX/XY).
- DNA: Double helix; nucleotides = Phosphate + Deoxyribose + Nitrogenous base (A, T, G, C).
- Replication: Semi-conservative (each daughter helix has one parental strand).
- RNA: Single-stranded; bases A, U, G, C; mRNA, tRNA, rRNA roles in protein synthesis.
5. Central Dogma (केंद्रीय सिद्धांत)
- DNA → (transcription) → mRNA → (translation) → Protein.
- Transcription: nucleus में; Translation: ribosome पर।
6. Mutation & Variation (विकृति और विविधता)
- Mutation: DNA में स्थायी परिवर्तन — point mutation, frameshift, chromosomal mutations (deletion, duplication, inversion, translocation).
- Mutations का प्रभाव: neutral, harmful, beneficial (rare)।
- Sources: spontaneous errors, mutagens (radiation, chemicals), UV light.
7. Genetic Disorders (आनुवांशिक रोग)
| Disorder | Cause / Inheritance | Key features |
|---|---|---|
| Down syndrome | Trisomy 21 (chromosomal) | Mental retardation, characteristic facies |
| Hemophilia | X-linked recessive | Blood clotting defect |
| Sickle cell anemia | Autosomal recessive (point mutation in β-globin) | Abnormal RBC shape, anemia |
| Cystic fibrosis | Autosomal recessive | Thick mucus, respiratory infections |
| Tay–Sachs | Autosomal recessive | Neurodegeneration in infants |
8. Pedigree Analysis (वंशावली चार्ट)
- Pedigree charts trace inheritance in families — squares (males), circles (females), shaded = affected.
- Useful to determine dominant/recessive and sex-linked patterns.
9. Genetic Engineering Basics (जेनिटिक इंजीनियरिंग)
- Recombinant DNA: DNA fragments joined using restriction enzymes & ligases.
- Vectors: Plasmids, bacteriophages used to insert DNA into host cells.
- Techniques: PCR (amplify DNA), Gel electrophoresis (separate fragments), DNA sequencing.
- Applications: Insulin production, GM crops, gene therapy, forensic DNA fingerprinting.
10. Biotechnology Terms — Handy Table
| Term | Meaning / Use |
|---|---|
| PCR | Polymerase Chain Reaction — amplify specific DNA segment |
| Restriction enzymes | Cut DNA at specific sequences |
| Gel electrophoresis | Separate DNA/RNA by size |
| Cloning | Produce genetically identical organisms/cells |
| Transgenic | Organism with foreign gene inserted |
11. Modern Concepts (संक्षेप)
- Epigenetics: Gene expression regulation without DNA sequence change (methylation, acetylation).
- CRISPR-Cas9: Precise gene editing tool (targeted cuts & edits).
- Gene therapy: Replace/repair defective genes to treat disease (experimental / clinical advances).
12. Quick Revision (One-Liners)
- Mendel: Segregation & Independent Assortment • Allele = gene variant.
- DNA = genetic code (A–T, G–C) • Replication semi-conservative.
- Mutation = source of variation • Not all mutations harmful.
- Sex-linked traits show different patterns in males/females.
- PCR, restriction enzymes, vectors — core tools of molecular genetics.
MCQs — 20 प्रश्न (उत्तर सहित)
- Mendel की Law of Segregation किस प्रक्रिया से जुड़ी है? — Meiosis (गैमेट्स बनना)
- DNA के आधार किस क्रम में होते हैं? — A-T, G-C
- Which molecule carries amino acids to the ribosome? — tRNA
- Human somatic cells में कितने chromosomes होते हैं? — 46
- Which technique is used to amplify DNA? — PCR
- Hemophilia का inheritance pattern क्या है? — X-linked recessive
- Which enzyme joins DNA fragments? — DNA ligase
- Which disorder caused by Trisomy 21? — Down syndrome
- Which blood group shows co-dominance? — AB
- Which mutation changes a single base? — Point mutation
- Which technique separates DNA fragments by size? — Gel electrophoresis
- Sickle cell anemia is caused by mutation in which protein? — Hemoglobin (β-globin)
- Which process converts DNA → RNA? — Transcription
- Which organelle helps in protein synthesis? — Ribosome
- Which term means same allele pair (AA or aa)? — Homozygous
- Which is a chromosomal mutation? — Deletion / Duplication / Inversion
- Which tool enables targeted gene editing? — CRISPR-Cas9
- Which genetic condition is X-linked dominant/recessive more common in males? — X-linked recessive (e.g., color blindness)
- Which is used as cloning vector in bacteria? — Plasmid
- Which term describes observable traits? — Phenotype
निष्कर्ष: Genetics परीक्षा-अनुकूल विषय है — Mendel के मूल सिद्धांत, DNA/RNA का ज्ञान, प्रकार की विरासत, आनुवंशिक रोग व आधुनिक जीन तकनीकें (PCR, cloning, CRISPR) बार-बार पूछे जाते हैं। ऊपर दी गई तालिकाएँ, One-liners और MCQs नियमित रिवाइज़ करें — सफलता मिलेगी।
Note: यह सार SSC/RRB स्तर हेतु उपयुक्त है; विषय का विस्तार molecular pathways, quantitative genetics और population genetics में किया जा सकता है यदि आप चाहें तो मैं आगे बढ़ाकर वह भी जोड़ दूँगा।