Topics
Sexual Reproduction in Flowering Plants
- Flower
- Pre-fertilisation in Flowering Plant: Structures and Events
- Structure and Development of Anther
- Microsporogenesis
- Structure and Development of Male Gametophyte
- Pollen Products
- Structure and Development of Ovule
- Megasporogenesis
- Development of Female Gametophyte or Embryo Sac
- Pollination
- Autogamy
- Geitonogamy
- Xenogamy
- Agents of Pollination
- Anemophily
- Hydrophily
- Animal-Mediated Pollination (Zoophily)
- Outbreeding Devices
- Pollen Pistil Interaction
- Artificial Hybridization or Artificial Fertilization
- Double Fertilization and Triple Fusion
- Post-Fertilization Structures and Events
- Endosperm
- Embryo
- The Seed
- Apomixis
- Polyembryony
Reproduction in Organisms
Reproduction
Human Reproduction
- Human Reproduction
- The Male Reproductive System
- The Female Reproductive System
- Gametogenesis
- Structure of Sperm
- Oogenesis
- Menstrual Cycle (Ovarian Cycle)
- Major Events of Menstrual Cycle
- Menstrual Hygiene
- Fertilization in Human
- Implantation in Human
- Pregnancy and Embryonic Development
- Parturition (Birth) in Human
- Lactation in Human
Genetics and Evolution
Reproductive Health
- Concept of Reproductive Health
- Population Explosion and Birth Control
- Birth Control
- Natural Contraceptive Methods
- Artificial Contraceptive Methods
- Induced Abortion or Medical Termination of Pregnancy (MTP)
- Sexually Transmitted Diseases (STD) or Sexually Transmitted Infections (STI)
- Infertility
- Assisted Reproductive Technology (ART)
- Amniocentesis
- Genetic Counselling
Biology and Human Welfare
Environmental Issues
- Controlling Vehicular Air Pollution: a Case Study of Delhi
- Effects of Domestic Sewage and Industrial Effluents on Water
- Solid Wastes
- Radioactive Wastes
- Greenhouse Effect and Climate Change
- Ozone Depletion in the Stratosphere
- Degradation by Improper Resource Utilisation and Maintenance
- Radioactive Waste Management and E-waste
Biotechnology
Principles of Inheritance and Variation
- Heredity and Variation
- Gregor Johann Mendel – Father of Genetics
- Mendel's Experiments on Inheritance
- Monohybrid Cross
- Punnett Square
- Back Cross and Test Cross
- Mendel's Laws > The Law of Dominance
- Mendel's Laws > The Law of Segregation (Law of Purity of Gametes)
- Exceptions to Mendel's Principles > Incomplete Dominance
- Exceptions to Mendel's Principles > Co-Dominance
- Dihybrid Cross
- Mendel's Laws > The Law of Independent Assortment
- Chromosomal Theory of Inheritance
- Linkage and Recombination
- Polygenic Inheritance
- Exceptions to Mendel's Principles > Pleiotropy
- Sex Determination
- Sex Determination in Humans
- Sex Determination in Honey Bees
- Mutations
- Pedigree Analysis
- Mendelian Disorders in Humans
- Chromosomal Disorders or Abnormalities
Ecology
Molecular Basis of Inheritance
- Deoxyribonucleic Acid (DNA)
- Structure of Polynucleotide Chain
- Packaging of DNA Helix
- Search for Genetic Material
- Griffith’s Experiment
- Avery, McCarty and MacLeod’s Experiment
- The Hershey-Chase Experiment
- Properties of Genetic Material
- The RNA World
- DNA Replication
- Conservative Replication
- Dispersive Replication
- Semi-Conservative Replication
- Meselson and Stahl’s Experiment
- Enzymes used in DNA Replication
- Mechanism of DNA Replication
- Protein Synthesis
- Reverse Transcription (Teminism)
- Transcription
- Transcription Unit and the Gene
- Process of Transcription in Bacteria
- Process of Transcription in Eukaryotes
- Genetic Code
- Characteristics of the Genetic Code
- Mutations and Genetic Code
- tRNA – the Adapter Molecule
- Translation
- Regulation of Gene Expression
- The Lac Operon
- Human Genome Project
- DNA Fingerprinting
Evolution
- Origin of Life on Earth
- Urey and Miller’s Experiment
- Evolution of Life Forms - a Theory
- Evidences Supporting the Theory of Evolution
- Adaptive Radiation
- Theories and Mechanism of Evolution
- Theories and Mechanism of Evolution
- Hardy Weinberg’s Principle
- Brief Account of Evolution
- Human Evolution
- Overview of Evolution
Human Health and Diseases
- Concept and Determinants of Health
- Modes of Transmission of Diseases through Pathogens
- Diseases Caused by Bacteria > Typhoid
- Diseases Caused by Bacteria > Pneumonia
- Diseases Caused by Viruses > Common Cold
- Diseases Caused by Protozoa > Malaria
- Diseases Caused by Protozoa > Amoebiasis (Amoeboic dysentery)
- Diseases Caused by Helminths > Ascariasis
- Diseases Caused by Helminths > Filariasis (Elephantiasis)
- Diseases Caused by Fungi > Ringworm
- Prevention and Control of Infectious Diseases
- Immunity
- Types of Immunity > Innate Immunity
- Types of Immunity > Acquired Immunity
- Active and Passive Immunity
- Vaccination and Immunization
- Allergies
- Autoimmunity
- The Immune System
- Acquired Immuno Deficiency Syndrome (AIDS)
- Cancer
- Causes of Cancer
- Symptoms and Diagnosis of Cancer
- Prevention/Treatment of Cancer
- Drugs and Alcohol Abuse
- Addiction and Dependence
- Effects of Drug and Alcohol Abuse
- Prevention and Control of Drugs and Alcohol Abuse
- Overview of Human Health and Diseases
Strategies for Enhancement in Food Production
Microbes in Human Welfare
- Microorganisms (Microbes) and Microbiology
- Microbes in Household Products
- Microbes in Industrial Products
- Microbes in Sewage Treatment
- Microbes in Production of Biogas
- Microbes as Biocontrol Agents
- Microbes as Biofertilizers
- Applications of Biotechnology in Health and Medicine
- Overview of Microbes in Human Welfare
Biotechnology - Principles and Processes
Biotechnology and Its Application
- Concept of Biotechnology
- Biotechnological Application in Agriculture
- Biotechnological Application in Medicine
- Transgenic Animals
- Bioethics
- Overview of Biotechnology and Its Application
Organisms and Populations
- Organisms and Their Environment
- Ecology
- Population Attributes
- Population Growth
- Life History Variation
- Population Interactions
- Negative Interactions > Predation
- Negative Interactions > Competition
- Negative Interactions > Parasitism
- Positive Interactions > Commensalism
- Positive Interactions > Mutualism (Symbiosis)
- Overview of Organisms and Populations
Ecosystem
Biodiversity and Its Conservation
Estimated time: 5 minutes
CBSE: Class 12
Definition: Linkage
The physical association of two or more genes located on the same chromosome, due to which they tend to be inherited together and do not assort independently, is called linkage.
CBSE: Class 12
Definition: Recombination
The process by which new (non-parental) combinations of genes are produced due to exchange of genetic material between homologous chromosomes during meiosis, is called recombination.
CBSE: Class 12
Key Points: Linkage and Recombination
- Linkage - physical association of two or more genes on the same chromosome; linked genes do not assort independently.
- Recombination - generation of non-parental gene combinations due to crossing over between linked genes.
- Morgan's dihybrid crosses in Drosophila showed the F₂ ratio deviated from 9:3:3:1; genes were located on the X chromosome.
- Genes on the same chromosome show more parental combinations than non-parental (recombinant) types.
- Tightly linked = low recombination (white & yellow = 1.3%); loosely linked = high recombination (white & miniature wing = 37.2%).
- Alfred Sturtevant (Morgan's student) used recombination frequency to measure gene distance and create chromosome maps, now used in Human Genome Sequencing.
