Heredity and Variation (वंशागती एवं विविधता) | Class 12 RBSE Biology Chapter 4

This video provides complete coverage of Heredity and Variation (वंशानुगति तथा विविधता) Chapter 4 from Class 12 RBSE Biology. This is a comprehensive study material designed specifically for RPSC competitive exam aspirants and board exam students. 🎯 EXAM IMPORTANCE: ✅ Board Exams: 8-10 marks ✅ RPSC School Lecturer: 10-15 questions ✅ RPSC 1st Grade Teacher: 8-12 questions ✅ RPSC 2nd Grade Teacher: 6-10 questions ✅ REET Level 1 and Level 2: 5-8 questions 📖 COMPLETE TOPICS COVERED: 1. GREGOR MENDEL - FATHER OF GENETICS Birth and death dates (July 20, 1822 - January 6, 1884) Experiments on Pisum sativum (Pea plant) 7 contrasting characters selected Why Mendel chose pea plant Work published in 1866 Rediscovery in 1900 2. MENDEL'S THREE LAWS OF INHERITANCE Law of Dominance with examples Law of Segregation (Purity of Gametes) Law of Independent Assortment Monohybrid cross: P, F1, F2 generations F2 Phenotypic ratio: 3:1 F2 Genotypic ratio: 1:2:1 Dihybrid cross complete explanation F2 ratio: 9:3:3:1 Punnett square method 3. INCOMPLETE DOMINANCE Definition and concept Example: Mirabilis jalapa (Four O'Clock plant) Cross between Red and White flowers F1: All Pink (intermediate) F2 ratio: 1:2:1 (Red:Pink:White) 4. CO-DOMINANCE Definition with examples ABO blood group system Three alleles: IA, IB, i 4 blood groups: A, B, AB, O 6 possible genotypes Universal donor: O group Universal recipient: AB group Rh factor (Rh+ and Rh-) 5. CHROMOSOMAL THEORY OF INHERITANCE Proposed by Walter Sutton and Theodor Boveri (1902) Genes located on chromosomes Supporting evidence 6. SEX DETERMINATION Human chromosome number: 46 (23 pairs) Autosomes: 44 (22 pairs) Sex chromosomes: XX (female), XY (male) XY system in humans ZW system in birds XO system in grasshoppers Father determines child's sex Sex ratio: 1:1 7. LINKAGE AND CROSSING OVER Discovered by Thomas Hunt Morgan (1910) Complete and incomplete linkage Crossing over process Occurs in Pachytene stage Recombination frequency Map units and centimorgan 8. MUTATION Definition by Hugo de Vries (1901) Somatic vs Germinal mutation Gene mutation vs Chromosomal mutation Beneficial, harmful, and neutral mutations Mutagens: Physical, Chemical, Biological 9. GENETIC DISORDERS Mendelian Disorders: Sickle Cell Anemia (Autosomal recessive, Chromosome 11) Thalassemia (Autosomal recessive) Hemophilia (X-linked recessive, Factor VIII and IX deficiency) Color Blindness (X-linked recessive, affects 8% males) Phenylketonuria/PKU (Autosomal recessive, Chromosome 12) Chromosomal Disorders: Down Syndrome (Trisomy 21, Karyotype: 47, +21) Klinefelter Syndrome (47, XXY in males) Turner Syndrome (45, XO in females) Edward Syndrome (Trisomy 18) Patau Syndrome (Trisomy 13) 10. PEDIGREE ANALYSIS Symbols and their meanings Autosomal dominant and recessive patterns X-linked inheritance patterns Uses in genetic counseling 11. IMPORTANT SCIENTISTS AND CONTRIBUTIONS Gregor Mendel (1866) - Laws of Inheritance Hugo de Vries (1900) - Rediscovered Mendel's work, Mutation Walter Sutton & Theodor Boveri (1902) - Chromosomal theory Thomas Hunt Morgan (1910) - Linkage and crossing over Karl Landsteiner (1900) - ABO blood groups F.A. Janssens (1909) - Crossing over 12. EXAM-IMPORTANT FACTS AND FORMULAE Mendel's experimental duration: 7 years (1856-1863) Number of pea plants used: 28,000 Test cross ratio: 1:1 Back cross definition Number of phenotypes formula: 2^n Number of genotypes formula: 3^n Number of gametes formula: 2^n Recombination frequency calculation Barr body discovered by Murray Barr (1949) #HeridityAndVariation #Class12Biology #RBSEBiology #RPSCExam #SchoolLecturer #1stGradeTeacher #2ndGradeTeacher #REET #BiologyInHindi #Vanshanugati #Genetics #MendelsLaws #RajasthanExams #CompetitiveExam #BoardExam #GeneticDisorders #SexDetermination #BloodGroups #DownSyndrome #Hemophilia #BiologyPreparation