LESSON 4 BIO

• Genetics


  The branch of biology that deals with the principles of heredity and variation in all living things
• Heredity


  Our genetic heritage, the passing of traits from the parents to their offspring
• Variation


  The differences in the genetic makeup or physical appearance of different organisms
• Branches of Genetics


  • Molecular Genetics
  • Developmental Genetics
  • Cytogenetics
  • Evolutionary Genetics
  • Biochemical Genetics
  • Behavioral Genetics
  • Population Genetics
  • Quantitative Genetics
• Applications of Genetics


  • Plant, Animal and Microbial Improvement
  • Medicine
  • Genetic counseling
  • Legal Applications
  • Recombinant DNA Technology
• Theory of Pangenesis


  Gemmules, small particles in the body, were formed everywhere and reflected the characteristics of the body part from where it was formed. They travelled through blood vessels into the male reproductive organ and were transmitted to the next generation.
• Theory of Inheritance of Acquired Characteristics


  Body modifications acquired by use or disuse could be transmitted to the offspring because the gemmules formed reflected such modifications
• Germplasm Theory


  Germplasm or sex cells perpetuated themselves in reproduction generation after generation, while somatoplasm or body cells were produced by germplasm to protect and reproduce itself
• Gregor Mendel


  • Member of the monastery in Czech Republic, taught physics, botany, and natural science courses at the secondary and university levels
  • Began a decade-long research involving the inheritance patterns of pea plants in 1856
  • Discovered that hereditary characteristics were determined by elementary factors that are transmitted between generations in 1866
• Mendelian Observation


  • Mendel was the first to follow single traits from generation to generation instead of trying to document and follow every trait in plants
  • He worked with traits that show discontinuous variation
  • He chose to work with garden pea plants (Pisum sativum) which gave him advantage
• Mendel's Experiment


  1. Confirmed that he was using true-breeding plants for white or violet flower color

  2. Applied the pollen from a plant with violet flowers to the stigma of a plant with white flowers

  3. Observed that 100% of the F1 hybrid generation had violet flowers

  4. Allowed the F1 plants to self-fertilize and found that 705 plants in the F2 generation had violet flowers and 224 had white flowers, a ratio of approximately 3:1

  
• Dominant and Recessive Traits


  Dominant traits are those that are inherited unchanged in a hybridization, while recessive traits disappear in the offspring of hybridization but reappear in the offspring of the hybrids
• Chromosome Theory of Inheritance

  • Chromosomes come in matched (homologous) pairs in an organism, like Mendel's genes
  • Segregation of pair factors (in Mendel's observation) is paralleled by the separation of homologous chromosomes during meiosis
  • Individual genes are found at specific locations on chromosomes, and the behavior of chromosomes during meiosis can explain why genes are inherited according to Mendel's observation

  
• Chromosomes


  Thread-like structures located inside the nucleus of the cell, made up of protein (histone) and DNA

  
• In 1903, Walter Sutton and Theodor Boveri independently suggested the association between Mendelian factors with chromosomes

  
• They stated that the segregation of pair factors (in Mendel's observation) is paralleled by the separation of homologous chromosomes during meiosis

  
• The individual genes are found at specific locations on chromosomes, and the behavior of chromosomes during meiosis can explain why genes are inherited according to Mendel's observation
• These observations proposed the Chromosome Theory of Inheritance
• Thomas Hunt Morgan confirmed this theory when he discovered the sex chromosomes on his study about fruit flies
• Observations that support the Chromosome Theory of Inheritance

  • Chromosomes, like Mendel's genes, come in matched (homologous) pairs in an organism
  • One of the pair come from the mother, and one from the father
  • The member of the homologous pair separates in meiosis, so that each sperm or egg has just one member
  • The members of different chromosome pairs are sorted into gametes independently of one another in meiosis, resembling the behavior of genes in Mendel's Law of Independent Assortment

  
• Centromere


  The constricted region of the chromosome that helps keep chromosomes properly aligned during cell division and the attachment site for the sister chromatids

  
• Telomeres


  Located at the ends of the chromosomes, they protect the ends of the chromosomes and sustain chromosome stability

  
• Short arm (p arm)


  One of the regions on either side of the centromere
• Long arm (q arm)


  One of the regions on either side of the centromere
• Types of Chromosome According to Position of Centromere

  • Telocentric
  • Acrocentric
  • Sub-metacentric
  • Metacentric

  
• Chromosomes are strongly stained when used in research
• The number of chromosomes is constant for a particular species
• Examples of chromosome numbers in different species

  • Humans: 23 pairs
  • Fruit fly: 4 pairs
  • Rice plant: 12 pairs
  • Dogs: 39 pairs
  • Cats: 19 pairs

  
• Sex chromosomes


  Females have two X chromosomes (XX) while males have one X and one Y chromosome (XY)

  
• The sex of the child is determined by the chromosome passed down by the male
• DNA (deoxyribonucleic acid)


  The genetic material that is passed from parents to offspring, containing the specific instructions that make each type of living creature unique
• In 1944, Oswald Avery, Colin MacLeod, and Maclyn McCarty concluded that DNA is the genetic material
• DNA was first identified in the late 1860s by Swiss chemist Friedrich Miescher
• Erwin Chargaff showed that there are four kinds of monomers (nucleotides) present in DNA molecule, where two types were always present in equal amount and the remaining two types were also present in equal amounts
• James Watson and Francis Crick concluded that the DNA is made up of two strands in the form of a double helix

  
• Nucleotides


  Made up of a pentose sugar (ribose or deoxyribose), a nitrogenous base (purines (G, A) and pyrimidines (C, T)), and phosphoric acid
• Complementary base pairs


  Cytosine (C) always pairs with Guanine (G), and Adenine (A) always with Thymine (T)
• Central Dogma


  The series of events from DNA to RNA to protein production
• DNA Replication


  1. Helicase unwinds the parental double helix

  2. Single-stranded binding proteins stabilize the unwound parental DNA

  3. The leading strand is synthesized continuously in the 5' to 3' direction by DNA polymerase

  4. The lagging strand is synthesized discontinuously in Okazaki fragments

  5. DNA ligase joins the Okazaki fragments to the growing strand

  
• Transcription


  1. DNA double helix partially unwinds in the region of mRNA synthesis

  2. RNA polymerase moves along the template strand, complementing DNA template nucleotides with RNA nucleotides

  3. A single-stranded RNA is produced until a termination point is reached