Chapter 2 Biology GCSE

• You have 46 chromosomes arranged in 23 pairs.
• Gametes only have 23 chromosomes.
• Chromosomes hold genetic information and instructions for making new cells
• The YY chromosomes is for female and XY for male
• Cell division is needed for growth.
• Mitosis is the cell division needed for repair and growth. It produces two identical daughter cells.
• The cell cycle is the following: chromosomes replicate themselves, they align themselves in the centre of the cell, spindle fibres pull them to opposite sides, and the cell splits leaving the membrane and cytoplasm, creating 2 identical daughter cells.
• The mitosis stage is the spindle fibres till the splitting,
• The process of making 2 identical daughter cells is called cytokinesis.
• The cell cycle takes 24 hours to complete
• Mitosis is only 10% of the cell cycle.
• A gene is a unit of DNA that codes for a protein
• A stem cell is an unspecialised cell that can divide to produce more cells of the same type.
• Embryo cells are stem cells.
• A differentiated cell is a cell that is specialised to complete a function.
• In mature animals, little to no differentiation happens.
• Differentiation happens all through out plants' lives.
• Plant cells don't differentiate until they reached the final position.
• Plant cells can re-differentiate into other cells.
• Producing identical offsprings is called cloning.
• Undifferentiated cells in active regions of roots and tip of shoots is called meristems.
• When a sperm cell and egg cell fertilise it forms a zygote cell.
• At day 5/6 in an embryo zygote cells begin to specialise
• There is an ethical issue with the usage of embryo cells: when the stem cells are obtained from the embryo is destroyed.
• Adult bone marrow cells can only differentiate to red blood cells, white blood cells and platelets.
• Stem cells can grow back insulin producing cells or motor neurons helping diabetes and paralysis.
• A zygote forms an embryo cell since it divides into smaller cells
• Therapeutic cloning is a good method since the body won't reject the cells because they're from the same person and have the same genes.
• Steps of therapeutic cloning: the nucleus is taken from a human cell, the nucleus is inserted into an egg cell, the egg cell is stimulated/shocked so the cell can develop into an embryo cell, the stem cell is taken from the embryo, and stem cell grows in a container in vetro(in glass), stem cell treated to develop into the required cell for the patient.
• Therapeutic cloning can: help create new organs,help with kidney issues, prevent disease, research.
• Why do we need mitosis

  growth and respiration
• Why is mitosis important

  Its needed for growth and repair