Genetics and Evolution

https://www.youtube.com/watch?v=NR3779ef9yQ -  An Introduction to Mendelian Genetics

https://www.youtube.com/watch?v=UeyYGeg-jDI -  Mendelian genetics and Punnett squares

https://www.youtube.com/watch?v=P0nMnPPdW_k -  Alleles and genes

https://www.youtube.com/watch?v=eEUvRrhmcxM&t=372s -  Introduction to Heredity

https://www.youtube.com/watch?v=OhYOfTczCk4 -  Mendelian inheritance and Punnett squares

https://www.youtube.com/watch?v=OVM68-0YVWI -  Co-dominance and Incomplete Dominance

https://www.youtube.com/watch?v=C8OL1MTbGpU - Genes vs. DNA vs. Chromosomes 

https://www.youtube.com/watch?v=s9HPNwXd9fk -  Chromosomes, Chromatids, Chromatin, etc.

 

 

CHAPTER 4: Principles of Inheritance and Variation

  • Genetics: Branch of biology dealing with inheritance and variation of characters from parents to offspring.
  • Inheritance: Process by which characters/traits are passed from parents to progeny (basis of heredity).
  • Variation: Degree by which progeny differ from their parents (arises mainly from sexual reproduction).
  • True-breeding line: Organisms that show stable trait inheritance after continuous self-pollination over generations.
  • Alleles: Slightly different forms of the same gene that code for a pair of contrasting traits.
  • Genotype: Genetic constitution of an organism (e.g., TT, Tt, tt).
  • Phenotype: Observable/expressed characteristics of an organism (e.g., tall or dwarf).
  • Dominant trait: Trait/factor that expresses itself in the heterozygous condition (e.g., T for tallness).
  • Recessive trait: Trait that expresses only in the homozygous condition (e.g., t for dwarfness).
  • Monohybrid cross: Hybridisation involving one pair of contrasting traits (e.g., tall × dwarf).
  • Dihybrid cross: Hybridisation involving two pairs of contrasting traits (e.g., seed shape and colour).
  • Law of Dominance: In a pair of dissimilar factors, one dominates the other (first law of Mendel).
  • Law of Segregation: Alleles separate during gamete formation; each gamete receives only one allele (second law).
  • Law of Independent Assortment: Genes for different traits segregate independently during gamete formation.
  • Punnett Square: Graphical method to predict genotypes and phenotypes of offspring in a cross.
  • Test cross: Cross between an individual of unknown genotype (showing dominant phenotype) and a homozygous recessive parent to determine genotype.
  • Linkage: Physical association of genes on the same chromosome (reduces recombination).
  • Recombination: Generation of new combinations of alleles due to crossing over.
  • Sex determination: Chromosomal mechanism deciding male/female (e.g., XX-XY in humans, ZZ-ZW in birds).
  • Mutation: Sudden heritable change in DNA sequence (raw material for evolution).
  • Genetic disorders: Diseases caused by gene/chromosome abnormalities (e.g., haemophilia, sickle-cell anaemia, Down’s syndrome).
  • Pedigree analysis: Study of inheritance patterns in family trees.
  • Polygenic inheritance: Traits controlled by multiple genes (e.g., human skin colour).
  • Pleiotropy: One gene influences multiple phenotypic traits.

CHAPTER 5: Molecular Basis of Inheritance

  • DNA (Deoxyribonucleic acid): Double-stranded helical polymer of deoxyribonucleotides; primary genetic material in most organisms.
  • RNA (Ribonucleic acid): Single-stranded nucleic acid; acts as messenger, adapter, and genetic material in some viruses.
  • Nucleotide: Basic unit of nucleic acid consisting of a nitrogenous base, a pentose sugar, and a phosphate.
  • Purines: Nitrogenous bases adenine (A) and guanine (G).
  • Pyrimidines: Nitrogenous bases cytosine (C), thymine (T in DNA), uracil (U in RNA).
  • Double helix model: Watson-Crick model of DNA structure (1953) with antiparallel strands and base pairing.
  • Base pairing / Chargaff’s rule: A pairs with T (2 H-bonds), G with C (3 H-bonds).
  • Central Dogma: Flow of genetic information: DNA → RNA → Protein.
  • Replication: Process of making exact copies of DNA (semiconservative mechanism).
  • Transcription: Synthesis of RNA from DNA template.
  • Translation: Synthesis of protein from mRNA on ribosomes.
  • Genetic code: Sequence of nucleotides (triplet codons) that specifies amino acids.
  • Codon: Triplet of nucleotides that codes for one amino acid.
  • tRNA (transfer RNA): Adapter molecule that brings amino acids to ribosome (clover-leaf structure).
  • Lac operon: Inducible operon in E. coli that regulates lactose metabolism (model for gene regulation).
  • Nucleosome: Basic unit of chromatin packaging; DNA wrapped around histone octamer.
  • Histones: Positively charged proteins around which DNA is wrapped in eukaryotes.
  • Chromatin: Thread-like structure of DNA and proteins in nucleus (euchromatin = active; heterochromatin = inactive).
  • Hershey-Chase experiment: Proved DNA (not protein) is the genetic material using radioactive bacteriophages.
  • Griffith’s transforming principle: Heat-killed virulent bacteria transform live non-virulent bacteria.
  • Avery, MacLeod, McCarty experiment: Identified DNA as the transforming substance.
  • Human Genome Project: International effort to sequence the entire human genome.
  • DNA Fingerprinting: Technique using VNTRs to identify individuals (forensic application).

CHAPTER 6: Evolution

  • Evolution: Gradual change in life forms over geological time leading to biodiversity.
  • Big Bang theory: Origin of universe through a massive explosion ~13.8 billion years ago.
  • Chemical evolution: Formation of organic molecules from inorganic precursors on early Earth (Oparin-Haldane hypothesis).
  • Miller’s experiment: Simulated early Earth conditions and produced amino acids, sugars, etc.
  • Spontaneous generation: Disproved theory that life arises from non-living matter (Pasteur’s experiment).
  • Natural selection: Mechanism proposed by Darwin; better-adapted individuals survive and reproduce more.
  • Fitness: Reproductive success of an individual/organism in its environment.
  • Branching descent: All existing life forms share common ancestors (common descent).
  • Adaptive radiation: Evolution of different species from a common ancestor in different habitats (e.g., Darwin’s finches).
  • Homologous organs: Structures with common ancestry but different functions (e.g., forelimbs of vertebrates).
  • Analogous organs: Structures with different ancestry but similar functions due to convergent evolution (e.g., wings of birds and insects).
  • Fossils: Remains of ancient organisms preserved in rocks (paleontological evidence).
  • Industrial melanism: Increase in dark-winged moths in polluted areas due to natural selection.
  • Hardy-Weinberg principle: Mathematical model of genetic equilibrium in a population (p² + 2pq + q² = 1).
  • Convergent evolution: Unrelated organisms develop similar traits in similar environments.
  • Divergent evolution: Related organisms evolve different traits in different environments.
  • Lamarckism: Theory of inheritance of acquired characters (use and disuse of organs).

Additional Cross-Cutting Keywords

  • Mendel: Father of genetics; proposed laws of inheritance through pea plant experiments.
  • Watson & Crick: Proposed double-helix structure of DNA (1953).
  • Darwin: Proposed theory of evolution by natural selection.
  • Chromosomal theory of inheritance: Genes are located on chromosomes (Sutton & Boveri).