Lecture Notes: Reproduction and Inheritance

Introduction

• Presenter: Andy from Med School EU
• Subject: Biology section for IMAT
• Main Focus: Reproduction and inheritance, starting with life cycles

Types of Life Cycles

1. Diploid Life Cycle (Animal Life Cycle)

   • Begins with a zygote (fertilized egg by sperm, diploid structure, 2n)
   • Zygote undergoes mitosis to form a fully grown organism
   • Most of the life cycle is spent in the diploid phase
   • Germ cells undergo meiosis to produce gametes (haploid phase, n)
   • Somatic cells continue mitosis without producing gametes
   • Humans have 46 chromosomes (23 pairs) in diploid state and 23 in haploid state

2. Alternating Generations (Plants, Some Fungi and Algae)

   • Fertilization produces a diploid sporophyte
   • Sporophyte undergoes meiosis to produce haploid spores
   • Spores undergo mitosis to produce gametophyte (haploid phase)
   • Gametophyte produces gametes, which fertilize to form a zygote
   • Mitosis occurs in both haploid (n) and diploid (2n) stages
   • Distinct from animal life cycles where mitosis does not occur in the haploid stage

3. Haploid Dominant (Other Fungi and Algae)

   • Begins with fertilization to form a zygote
   • Zygote undergoes meiosis producing haploid spores
   • Spores undergo mitosis to form gametophyte
   • Gametophyte undergoes mitosis to produce gametes, which fertilize
   • Dominant life cycle phase is haploid (most of the time organisms are in gametophyte form)
   • Opposite of the diploid-dominant animal life cycle

Key Differences

• Animal Life Cycle: Diploid dominant; no mitosis in haploid phase
• Plant/Alternating Generations: Mitosis in both phases
• Fungi/Algae Haploid Dominant: Most time spent in haploid phase

Next Topics

• Skip sexual and asexual reproduction (previously covered)
• Move to Genetics focusing on Mendelian Genetics and Gregor Mendel’s laws