Cell cycle

• Meiosis 1


  1. Produces 2 daughter cells

  2. Repeats the cycle once more to have 4 daughter cells
• Stages of meiosis 1 and 2

  1. Prophase

  2. Metaphase

  3. Anaphase

  4. Telophase
• Prophase


  • A new spindle fiber forms around the chromosomes
• Metaphase


  • Chromosomes line up at the equator
• Anaphase


  • Centromeres divide, chromatid moves to the opposite sides of the cells
• Telophase

  • A nuclear envelope forms around each set of chromosomes
  • The cytoplasm divides
• GENETICS IS THE STUDY OF HEREDITY AND VARIATION. IT AIMS TO UNDERSTAND HOW TRAITS CAN BE PASSED ON TO THE NEXT GENERATION AND HOW VARIATION ARISES.
• EVERY LIVING THING UNDERGOES REPRODUCTION. THE NUTRIENTS TAKEN BY AN INDIVIDUAL WILL PROVIDE FOR ENERGY FOR METABOLIC PROCESSES, FOR GROWTH AND DEVELOPMENT AS WELL AS REPRODUCTION. THE CELLULAR LEVEL OF REPRODUCTION, IN THE FORM OF CELL DIVISION, PROVIDES FOR THE BACKDROP FOR THE ORGANISMAL LEVEL OF REPRODUCTION
• HUMANS SHARE ABOUT 90% OF GENETIC MATERIAL WITH MICE AND 98% WITH CHIMPANZEES
• ALL LIVING THINGS CONTAIN WHAT WE CALL THE GENETIC MATERIAL THAT SERVES AS THE SET OF INSTRUCTIONS THAT DIRECT THE ACTIVITIES AND FUNCTIONS OF THE CELLS. THESE GENETIC MATERIALS, ALSO KNOWN AS THE DEOXYRIBONUCLEIC ACID OR DNA, ARE PASSED ON FROM ONE GENERATION TO THE NEXT TO ENSURE THE CONTINUITY OF LIFE.
• Cell Cycle


  1. Cell growth

  2. Duplication of Genetic material (DNA)

  3. Cell division (Splits into two or four new cells)
• Interphase


  G1, S, G2
• 1. phase


  Mitosis and meiosis
• G1-phase


  First gap period where the cell grows initially
• 1. phase


  Synthesis stage characterised by protein and ribonucleic acid (RNA) synthesis. RNA, which is synthesized based on the DNA, is then used to synthesize proteins. The middle stage of interphase, called the synthesis stage or S, is the period of DNA synthesis or replication. The chromosomes are duplicated in preparation for the next cell division.
• G2-phase

  Second gap period representing a period of rapid cell growth to prepare for cell division. During interphase, the nucleus is clearly visible as a distinct membrane bound organelle.
• 1. phase: Cell division


  1. Mitosis - This type of cell division produces two identical cells with the same number of chromosomes.

  2. Meiosis - A special type of cell division where the cell undergoes two rounds of cell division to produce four daughter cells, each with half the chromosome number as the original parent cell and with a unique set of genetic material as a result of exchange of chromosome segments during the process of crossing over.
• Stages of mitosis


  1. Prophase - The nuclear membrane and nucleoli may still be present. The chromosomes are thicker and shorter because of repeated coiling. At this stage, each chromosome is made up of two identical sister chromatids as a consequence of replication of DNA during the S phase.

  2. Metaphase - The nuclear membrane has disappeared while the highly coiled chromosomes align at the metaphase plate, an imaginary plane equidistant between the cell's two poles. Spindle fibers are also formed. Each fiber binds to a protein called the kinetochore at the centromere of each sister chromatid of the chromosome.

  3. Anaphase - The paired centromeres of each chromosome separate towards the opposite poles of the cells as they are pulled by the spindle fibers through their kinetochores. This liberates the sister chromatids. Each chromatid is now regarded as a full-fledged chromosome and is only made up of one sister chromatid.

  4. Telophase - The chromosomes are now at the opposite poles of the spindle. They start to uncoil and become indistinct under the light microscope. A new nuclear membrane forms around them while the spindle fibers disappear. There is also cytokinesis or the division of the cytoplasm to form two separate daughter cells immediately after mitosis.
• Humans share about 90% of genetic material with mice and 98% with chimpanzees
• Genetics


  The study of heredity and variation, aims to understand how traits can be passed on to the next generation and how variation arises
• Reproduction


  The nutrients taken by an individual will provide for energy for metabolic processes for growth and development as well as reproduction
• Genetic material


  Also known as deoxyribonucleic acid (DNA), serves as the set of instructions that direct the activities and functions of the cell and are passed on from one generation to the next
• Cell cycle


  A series of steps that includes cell growth, duplication of genetic material, and cell division usually resulting in identical cells
• Cell cycle


  1. Interface (G1 phase, S phase, G2 phase)

  2. M phase (Mitosis or Meiosis)
• G1 phase


  • Time the cell grows initially
• S phase


  • Characterized by protein and ribonucleic acid (RNA) synthesis, which is synthesized based on the DNA and then used to synthesize proteins
• G2 phase


  • Period of rapid cell growth to prepare for cell division
• Mitosis


  1. Prophase

  2. Metaphase

  3. Anaphase

  4. Telophase
• Meiosis


  1. Meiosis I (Prophase I, Metaphase I, Anaphase I, Telophase I)

  2. Meiosis II (Prophase II, Metaphase II, Anaphase II, Telophase II)
• Cell division plays a vital role in preserving life, allowing for growth, repair, and reproduction
• Cell division

  1. Protophase

  2. Metaphase

  3. Anaphase

  4. Telophase

  5. Telophase
• Protophase

  • Nuclear membrane and nucleoli are present
  • Cells are thicker and thinner due to repeated coiling
• Metaphase

  • Nuclear membrane disappears
  • Spindle fibers form
  • Pairs of centers of each cell separate, forming a full-fledged cell
• Telophase

  • Cells uncoil and become distinct under light microscopy