B5 | Mind Map

Cell Organisation in animals
1. Cells of the same type are organised into tissues
2. Different tissues work together and are grouped together to form organs
3. Organs work together as body systems
4. Organisms begin life as a zygote - a fertilised egg
5. The zygote divides by mitosis to form an embryo
6. In humans up to and including the 8 cell stage all the cells are identical. These cells are embryonic stem cells
7. After the 8 cell stage the cells become specialised and different tissues form
8. In adults stem cells remain in certain parts of the body. They can only differentiate into certain cell types
9. In specialised cells, only the genes are needed to enable that cell to function, as that type of cell is switched on
Cell specialisation in Plants
1. Specialised plant cells from tissues such as the xylem, which transports water and mineral salts, and phloem, which transports the products of photosynthesis
2. Tissues are organised into organs eg stems flowers etc...
3. Cells in regions called meristems are unspecialised
4. When meristem cells divide into 2 the new cell produced can differentiate into different cell types (the other stays a meristem cell)
5. Meristems produce growth and height and width
Plant Clones
1. New plants can be grown by placing the cut end of a shoot in water or soil
2. Roots grow at the base of the stem, while the shoot continues to grow
3. Pieces of plants that have meristems and are used to produce clones are called cuttings
4. Cuttings
  1. Can be used to produce new plants with the same desirable features as the parent
  2. Produce clones that are genetically identical to the parent plant
5. Root growth in cuttings is promoted by plant hormones
6. Another method of cloning is called tissue culture - a small piece of tissue or a few cells are placed on agar jelly containing nutrients and plant hormones, this makes it grow into a small plant
7. Plant hormones called auxins are included in the agar for tissue culture and in hormone rooting powder
8. Auxins increase cell division and cell enlargement, promoting growth of the plant tissue
Plant growth and development
1. Plant growth and development is affected by the environment
2. Plants response to the direction of light is called phototropism
3. Plants grow towards the light so they are positively phototropic
4. By growing towards light plants increase their chances of survival
5. The plant hormone called auxin is produced in the growing tip of plant shoots. It moves down the shoot and produces growth below the tip
6. If a plant is illuminated by one side
  1. The auxin produced in the tip is distributed towards the shaded side
  2. The auxin produces growth on the shaded side
  3. The shoot grows towards the lights
Mitosis
1. Is the type of cell division that makes something grow
2. Mitosis results in 2 daughter cells coming from the original cell which are genetically identical
3. Process
  1. 1. Before mitosis the DNA in each chromosome is copied, each chromosome doubles itself
  2. 2. The chromosomes line up in the middle of the cell
  3. 3. One chromosome of each pair go into each daughter cell
  4. BEFORE mitosis the cell increases in size, the number of organelles increase
Meiosis
1. Is the cell division used to produce gametes (sex cells) sperm and egg cells
2. In humans, gametes only contain 23 chromosomes not 46
3. Meiosis produces 4 daughter cells
4. Process
  1. 1. The chromosomes are duplicated and they pair up (like in mitosis)
  2. 2. The cell divides into 2
  3. 3. Those cells again divide into 2 to produce 4 daughter cells
Chromosomes, genes and DNA
1. Chromosomes
  1. Are thread-like structures found in the nucleus
  2. Are made from a DNA molecule
  3. Can be grouped into pairs (pairs of 23 in humans)
2. DNA
  1. A DNA molecule is a double helix
  2. The DNA molecule is 2 strands facing eachother
  3. The strands of DNA are made up of units linked by chemicals called bases
  4. There are 4 bases A, T, G, C
  5. T links with A - AT TA
  6. G links with C - GC CG
  7. The order of the bases in a gene makes up the genetic code. Which gives instructions for the creation of proteins
Protein Synthesis
1. It occurs in the cytoplasm
2. Messenger RNA (mRNA) is produced in the nucleus, using DNA as the template
3. mRNA carries the instructions for the assembly of proteins into the cytoplasm
4. Proteins are assembled on organelles in the cytoplasm called ribosomes
5. The number and the sequence of amino acids determines the type of protein and its properties
6. The sequence of amino acids in the protein is determined by its genetic code
7. The bases work in threes (base triplets) to code for an amino acid
8. mRNA is a copy of the base sequence of the DNA that makes up a gene
9. The mRNA leaves the nucleus and attaches to a ribosome
10. Transfer RNA (tRNA) ferry amino acids to the ribosome where they are bonded together to form proteins
Switching genes on and off
1. The cell only produces the proteins it needs to carry out its function
2. The genes to make these proteins are switched on; the others are switched off
3. Up to the 8 cell stage of the embryo the cells are the same
4. The cells produced in the division of embryonic stem cells undergo differentiation to produce specialised cells
5. Specialised cells begin to make specific proteins. They usually change shape and structure. eg muscle cells must produce the proteins needed to contract
6. In embryonic stem cells any gene can be switched on so it can produce any type of cell
7. Embryonic stem cells (and adult stem cells) therefore have the potential to replace cells needed to replace damaged tissues
Stem cell research and therapy
1. Stem cells are used to produce new cells to replace damaged or diseased cells
2. Using embryonic stem cells raises ethical issues because in removing cells the embryo is destroyed
3. According to some, embryos have a right to life from when they're conceived
4. Embryonic stem cells are normally removed in - in vitro fertilisation
5. The creation of embryos produced with the intention of destroying them would be even more controversial
6. Therapeutic cloning
  1. It overcomes some ethical issues of using embryonic stem cells
  2. It involves replacing the nucleus of an egg by the nucleus of a body cell
  3. And stimulating the egg cell to divide to produce an embryo
  4. This technique doesnt require fertilisation and the cells will be genetically identical to the patient so it won't be rejected by the immune system. But the embryo is still destroyed
  5. Using chemical treatment, scientists have managed to transform mammal body cells to stem cell

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	Created by Fin Carson about 8 years ago