CELL REPRODUCTION

• Life starts with a single zygote in a mother's womb
• Mother's haploid cells (23 chromosomes) + Father's haploid cells (23 chromosomes) = diploid daughter cell (46 chromosomes)
• A zygote can form multicellular organisms
• Cell division - is the key to growth and development. This process repair worn-out tissue
• The first ever prokaryotic cell existed 3.5 billion years ago (LUCA)
• LUCA - Last Universal Common Ancestor (the first living thing that existed on earth)
• Eukaryotic cell evolved from prokaryotic cell.
• Sperm (23 chromosomes) + Egg cell (23 chromosomes) = Zygote (46 chromosomes)
• Reproductive cells are haploid cells

  Fertilized cell (zygote) are diploid cells
• 2 separate sperm fertilize 2 separate eggs forming 2 separate zygotes - TWINS
• Sperm + Egg cell = Zygote - MEIOSIS

  Each zygote goes through MITOSIS creating 2 separate babies (twins) that can have opposite/same sex
• Fraternal twins - twins that are not identical and has separate placentas. They share 50% of genes.

  • 2 eggs + 2 sperms = 2 zygote
• Identical twins - twins that are genetically the same, share placenta and blood type.

  • 1 egg + 1 sperm = 1 zygote that will split in half (mitosis) so the share 100% of genes and are identical
• Ovaries - female reproductive organ that produces egg cell (ova)
• Fallopian tube/oviduct - site where egg cells are fertilized by sperm cells
• Uterus - womb (Layman's term) - where the embryo develops into a baby
• When egg is not fertilized, it will shed as menstruation
• Testes - produce sperm and testosterone, located in the scrotum
• Scrotum - A sac that holds the testes and is covered by skin.
• Interphase - in this phase of cell cycle, chromosome is in thread-like structure called chromatin
• Interphase - called the non-dividing phase because it is a period of growth
• 3 PHASES IN INTERPHASE

  Gap 1 - when cell produces macromolecule (protein, lipids, carbohydrates, nucleic acids)

  • when cellular components (organelles) increase in number.
• CHON - Carbon, Hydrogen, Oxygen, Nitrogen
• 3 PHASES IN INTERPHASE

  Synthesis - when DNA replication happen
• 3 PHASES IN INTERPHASE

  Gap 2 - when cell continue to grow, enzymes are synthesized, and proteins are organized into spindle fibers
• Mitotic phase - Karyokinesis (PMAT) and Cytokinesis happens during this phase
• Prophase - is a mitotic phase when the chromatin condenses and the nuclear envelope breaks down
• EARLY PROPHASE

  • when spindle fibers are formed but are not already attached to centromeres
  • chromosomes made of two sister chromatids form
  • nuclear membrane BEGINS disappearing
• LATE PROPHASE

  • when nuclear membrane already disappeared
  • there is a presence of centromere
• Metaphase - when double-stranded chromosomes are attached to centromere and these chromosomes are aligned towards the equator
• Prometaphase - when the condensed chromosomes become sequentially attached at their kinetochores (special protein) to the spindle microtubules.
• Anaphase - when centromeres break apart and sister chromatids separate
• In anaphase, pinching of plasma membrane and cytoplasm can be observed
• Telophase - separation of nucleus
• Centriole - is where spindle fibers originate, and only found in animal cell
• Original cell - parent cell

  New cell - daughter cells
• Body chromosomes of an organism are identical in somatic cells and are different in gametes
• BODY CELLS: Stomach and skin cells both have 46 chromosomes
• Mitosis is a type of Asexual Reproduction that produces genetically identical daughter cells

  • EX: Bacteria (unicellular) that divides through BINARY FISSION
• Meiosis involves gametes (sperm and egg cells) and produces four haploid cells