BIOB11 - LECTURE 1

  • Mitosis vs. Meiosis: Mitosis results in two identical daughter cells, used for growth and repair. Meiosis produces four genetically different haploid cells, essential for sexual reproduction. Key differences lie in chromosome behavior during division and the final products.

  • Functions in Meiosis:

    • Mitotic Spindle: Facilitates chromosome movement and segregation.

    • Microtubules: Components of the spindle, providing structural support and movement.

    • Kinetochores: Protein structures on chromosomes where microtubules attach.

    • Cohesins: Hold sister chromatids together until anaphase.

    • Centromeres: Regions where sister chromatids are most closely attached; crucial for chromosome segregation.

  • Law of Segregation: During gamete formation, allele pairs separate, ensuring each gamete carries only one allele per gene.

  • Law of Independent Assortment: Alleles of different genes assort independently during gamete formation if these genes are on different chromosomes or far apart on the same chromosome.

  • Genotypes:

    • Homozygous: Having two identical alleles for a gene (e.g., AA or aa).

    • Heterozygous: Having two different alleles for a gene (e.g., Aa).

  • Laws of Inheritance: Mendel's laws explain how traits are passed from parents to offspring, based on allele segregation and independent assortment during meiosis.

  • Predicting Genotypes/Phenotypes: Using tools like Punnett squares to predict offspring genotypes and phenotypes based on parental genotypes.

  • Crossing Over: Exchange of genetic material between homologous chromosomes during prophase I of meiosis, leading to genetic recombination.

  • Early DNA Experiments: Experiments by scientists like Griffith, Avery, MacLeod, and McCarty demonstrated that DNA, not protein, carries heritable information.

  • DNA Structure: DNA consists of a double helix composed of nucleotides with a sugar-phosphate backbone and nitrogenous bases (adenine, guanine, cytosine, thymine).

  • Purines vs. Pyrimidines:

    • Purines: Adenine (A) and guanine (G), which have a double-ring structure.

    • Pyrimidines: Cytosine (C) and thymine (T), which have a single-ring structure.

  • Nucleotides vs. Nucleosides:

    • Nucleosides: Sugar + nitrogenous base.

    • Nucleotides: Nucleoside + phosphate group(s).

  • Base Pairing: Adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C). This complementarity is crucial for DNA replication and transcription.

  • DNA Structure & Function: The double helix structure allows DNA to store and transmit genetic information accurately.

  • Organisms Using DNA: All cellular life forms (bacteria, archaea, and eukaryotes) use DNA as their primary genetic material.

  • Germline vs. Somatic Mutations:

    • Germline mutations: Occur in germ cells and can be passed to offspring.

    • Somatic mutations: Occur in somatic cells and are not heritable.

  • Central Dogma: Describes the flow of genetic information from DNA to RNA (transcription) to protein (translation).