Biology

• Genetic Engineering Process


  Enzymes are used to cut a gene out of a chromosome

  Same enzyme is then used to cut a vector which is usually a bacterial plasmid or virus

  Vector is used to put the gene in required cells

  If the gene is delivered into cells before they have differentiated (at the egg or embryo stage), all cells in the developed organism will have the gene and show the characteristic
• Meiosis

  Copies of the genetic information are made

  The cell divides twice to form 4 gametes each with 23 chromosomes

  All gametes are genetically different from each other and to the parent
• Mitosis Stages

  Growth - Before a cell can divide it needs to grow and increase the number of sub-cellular structures such as ribosomes and mitochondria

  DNA Synthesis - The DNA replicates to form two copies of each chromosome

  Mitosis - One set of chromosomes is pulled to each end of the cell and the nucleus divides. Then the cytoplasm and cell membranes divide to form two cells that are identical to the parent cell
• Human Embryo Stem Cells


  Can be cloned and made to differentiate into most different types of human cells
• Human Adult Stem Cells 


  Can form many (not all) types of cells including blood cells
• Human stem cells can be used to help treat disease like diabetes and paralysis
• Embryos produced by therapeutic cloning have the same genes as the patients meaning that they are not rejected by the patients body and is why they can be used for medical treatments
• Sperm cells

  Function is to fertilise an egg

  Streamlined with a long tail to swim to the egg

  Acrosome in the head containing enzymes to digest the cell membrane

  Large number of mitochondria in the mid section to release energy for movement
• Nerve cells

  Function is to carry electrical signals

  Long to carry signals long distance

  Branched connections to connect to other nerve cells and form a network around the body

  Insulating sheath to enhance transmission of electrical signals
• Muscle cells

  Function is to contract to allow movement

  Contain a large number of mitochondria to release energy from respiration for movement

  Long so that there is enough space to contract
• Undifferentiated stem cells in plants are grouped together in structures called meristems
• Stem cells from meristems in plants can be used to produce clones of plants quickly and economically..

  • Rare Species - can be cloned to prevent extinction
  • Crop Plants - with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers
• Root hair cells

  Function is to absorb water and minerals from the soil

  Hair like projections to increase the surface area

  No chloroplasts as they are in the soil and thus do not need them
• Xylem cells

  Function is to carry water and minerals in plants

  Form hollow xylem tubes made of dead tissue

  Long cells with walls toughened by lignin

  Water and minerals flow from the roots towards the leaves only in one direction in a process called transpiration
• Osmosis is the diffusion of water from an area of low concentration to an area of high concentration through a partially permeable membrane until both sides reach equilibrium
• Hypertonic Osmosis

  More concentrated solution than in the cells

  Net movement will be out of the body and into the solution
• Isotonic Osmosis


  Same concentration in the solution as in the cell
• Hypotonic Osmosis

  More concentrated solution in the cells rather than the new solution

  Net movement of particles will be into the cell

  In an animal cell this can cause it to burst due to the fact that it has no cell wall
• Factors which affect diffusion

  Concentration gradient

  Temperature

  Surface area of the membrane
• Diffusion is net movement of particles from a region of higher concentration to an area of lower concentration
• Active transport acts differently than osmosis as it does the opposite by taking in minerals from an area of high concentration to an area of lower concentration

  Additionally, it requires 1 ATP in order to be completed and is provided through respiration
• 3 main criteria a drug has to reach before being released to the public

  Dose

  Efficacy

  Toxicity
• Benign tumour


  Stays in a specific part of the body, often within a membrane
• Malignant tumour


  Spread throughout the body in the blood, leading to the creation of more secondary tumours
• Gene


  Small section of DNA on a chromosome
• Benefits of understanding the human genome


  Allows us to search for genes that are linked to disease

  Allows us to understand and treat inherited disorders

  Tracing human migration patterns from the past
• Alleles 


  Different versions of a gene
• Genotype 


  Tells us the present alleles
• Phenotype 


  Tells us the characteristics caused by the person's alleles
• Gene Therapy 


  The process of which scientists may be able to correct faulty alleles and treat inherited disorders
• Evolution 


  Change in inherited characteristics of a population over time through a process of natural selection
• Species can evolve to be so different that they can no longer interbreed to produce fertile offspring

  This is when the changed member of the species becomes a new species entirely
• Fossils can form if the following conditions are met..

  Too cold for decay

  Not enough oxygen for decay

  Not enough water for decay
• Linnaeus Classification System

  Kingdom

  Phylum

  Class

  Order

  Family

  Genus

  Species
• Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes
• Automatic control systems have..

  Stimulus

  Receptor

  Coordination centre

  Effector

  Response
• FSH causes an egg to mature in the ovary
• LH causes the egg to be released from the ovary
• Oestrogen and progesterone are involved in maintaining the uterus lining incase the egg is fertilised and implants itself in the womb
• Progesterone stops the pituitary gland from releasing FSH and LH