Lesson 2

• Chromosomes will only be visible under G2
• Structure of chromosome is composed of chains of nucleosomes
• Nucleosome core consists of H2A + H2B also called as Histones
• Chromosome also has chromatin fiber
• Centromere is also known as the primary constriction
• Nucleolus Organizer Region is responsible for ribosomal DNA
• Genome refers to complete set of genes
• Somatic chromosome number is diploid number of chromosomes
• Gametic Chromosome Number is the haploid number
• Mitosis is equational division
• Mitosis is composed of identical cells
• Prophase is when chromosomes are visibly composed of sister chromatids
• Metaphase: chromosome align at equatorial plane
• Anaphase: Separation of sister chromatids
• Telophase: regrouping of chromosomes after cytokinesis, 2 cells are formed
• Leptotene : thin thread
• Zygotene : homologous pairing
• Chiasmata holds bivalence together
• Formation of bivalent (II) happens at zygotene
• Meiosis I : reductional divisob
• Pachytene is the crossing over stage
• Pachytene results to genetic recombination
• Diplotene bivalence separates
• Diplotene is terminalization of chiasmata
• Diakinesis is where bivalence is evenly distributed
• Diakinesis is best stage to establish chromosome number
• Anaphase I is responsible for reductional division
• Metaphase is alignment of BIVALENCE
• Two haploid cells form at end of telophase I
• Non-chromatid exchange happens in pachytene
• Four haploid cells are formed in Telophase II
• Meiosis has timing when to occur:

  • Gametic or Terminal

  • Zygotic or Initial

  • Sporic or Intermediary
• Gametic or Terminal means meiosis will happen before gamete formation
• Sporic or Intermediary means meiosis is occurring in between diploid and gametic stage
• Zygotic or Initial means meiosis will be occuring after zygote formation.