Lecture Notes: General Biology Chapter 2 - Reproduction

Corrections from Previous Lecture

• Histone Proteins: Corrected to lysine and arginine (positively charged), not histidine.
• Bond Dissociation: Corrected to heterolytic bond dissociation (bond breaks into two), not homolytic.

Overview of Reproduction

• Covers both macro reproduction and cellular reproduction.
• Focus on how cells transition from one generation to the next.

Cellular Reproduction

The Cell Cycle and Mitosis

• Mitosis: Process of cell division.

  • Autosomal cells: Diploid (2 copies of each chromosome).
  • Germ cells: Haploid.
  • Mitosis: Diploid cells divide to form two diploid cells.

• Chromosomes:

  • Chromosomes are usually single-stranded, become double-stranded during DNA synthesis before mitosis.
  • Germ cells need to be haploid (n chromosomes) to form a 2n organism upon fusion.
  • Humans: Germ cells have 23 chromosomes, somatic cells have 46.

Genetic Variation

• Meiosis vs. Mitosis:

  • Meiosis involves genetic variation and germ cell formation.

• Meiosis:

  • Separation of homologous chromosomes (meiosis I) and sister chromatids (meiosis II).
  • Increases genetic diversity through crossing over.

Cell Cycle Phases

• Interphase: G1, S, G2 phases.

  • G1 Phase: Cell grows, organelle replication, restriction point checks readiness for S phase.
  • S Phase: DNA synthesis, chromosomes become double-stranded.
  • G2 Phase: Quality control, checks DNA replication occurred correctly.
  • M Phase: Mitosis, cell division.

• Regulatory Mechanisms:

  • Cyclins and cyclin-dependent kinases regulate cycle progression.
  • p53 gene: Important for DNA error checking, preventing cancer.

Mitosis Phases

• Prophase: Chromatin condenses, nuclear membrane dissolves.
• Metaphase: Chromosomes align at metaphase plate, spindle fibers attach.
• Anaphase: Sister chromatids pulled apart.
• Telophase: Cytokinesis occurs, new nuclear membrane forms.

Meiosis Process

Meiosis I

• Prophase I: Homologous chromosomes pair, crossing over occurs.
• Metaphase I: Homologous pairs line up.
• Anaphase I: Homologous chromosomes separate.
• Telophase I: Cells prepare for meiosis II.

Meiosis II

• Similar to mitosis with separation of sister chromatids.

Genetic Variations

• Crossing Over: Increases genetic diversity.
• Non-disjunction: Errors can lead to genetic disorders such as Down syndrome.

Male Reproductive Anatomy

• Testes: Produce sperm and testosterone.
• Epididymis: Stores sperm.
• Vas Deferens: Transports sperm.
• Seminal Fluid: Produced by seminal vesicles, prostate, and Cowper's gland.

Female Reproductive Anatomy

• Ovaries: Contain follicles, site of oogenesis.
• Fallopian Tubes: Site of fertilization, lined with cilia.
• Uterus: Muscular organ, site for potential embryo implantation.
• Cervix and Vagina: Connects uterus to the outside of the body.

X-linked Inheritance

• Colorblindness: Example of x-linked recessive trait.
  • Males inherit x-linked traits from mothers.
  • Females with x-linked condition must have affected fathers.

Miscellaneous

• Lecture Style: Informal, interactive, and relies heavily on participation and questions.
• Preparation for Exams: Emphasizes understanding key concepts over memorizing details.