B5 Growth and Development Summary

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  • Created by: Farhana
  • Created on: 27-12-12 18:49
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  • DNA
    • A DNA molecule has 2 stands shaped in a DOUBLE HELIX
      • Each strand is made up of nucleotides
        • Nucleotides has 4 bases- Adenine, Cytosine, Guanine, Thymine (base pairing: A-T, C-G)
          • Each set of 3 bases(triplet) codes for one amino acid
            • Cells make proteins by joining amino acids together in a particular order
    • Genes are sections of DNA that contains instruction for 1 particular protein
      • Proteins are made by organelles called RIBOSOMES in the cytoplasm
        • Cells make proteins by joining amino acids together in a particular order
    • DNA's found in the nucleus and can't move out because it's too big
      • A copy of the DNA's made by a mRNA- shorter single strand of DNA to get copies to ribosome
        • Proteins are made by organelles called RIBOSOMES in the cytoplasm
      • Chromosomes
        • Nucleus
          • Cell
            • New cells are needed for GROWTH & REPAIR produced by MITOSIS
            • Cells divide by MEIOSIS to produce gametes in 2 divisions
              • MEIOSIS PRODUCES CELL WHICH HAVE HALF THE AMOUNT OF CHROMOSOMES
                • Before cell divides, copies DNA. 1 arm of each chromosome clone of other arm
                  • 1st DIVISION: chromosome pairs line up in centre of cell
                    • Pairs pulled apart- each new cell has only 1 copy of each chromosome. Some of Dad's, some of Mum's in each new cell
                      • 2nd Division:  chromosomes line up again in centre of cell- arms pulled apart
                        • Results in 4 gametes each w/ only a SINGLE set of chromosomes in
            • Embryonic stem cells are undifferentiated up to the 8-cell stage
              • Replaces ANY faulty cells in sick people
              • Cloning used to make stem cells- nucleus of body cell into 'empty' egg cell
                • Adult stem cells used to cure diseases extracting stem cells from bone marrow
            • Adult stem cells used to cure diseases extracting stem cells from bone marrow
            • Meristem tissues(in shoots & roots, where growing) contain stem cells
              • Can divide and form organs for as long as plant lives
              • Cuttings of meristems cells can produce clones with ROOTING powder to help it grow into complete plants
              • Auxins are plant growth hormones (chemicals) that control growth near the tips of shoots & roots
                • When a shoot has more light, more auxins move to shaded side =cells elongate faster on shaded side= grow towards light
                  • Phototropism is growth Towards or Away from light
                    • Positive phototropism: leaves, need light for photosynthesis= food. Grow towards light
                      • When a shoot has more light, more auxins move to shaded side =cells elongate faster on shaded side= grow towards light
                        • Phototropism is growth Towards or Away from light
                          • Positive phototropism: leaves, need light for photosynthesis= food. Grow towards light
                            • Negative phototropism: roots, need nutrients + water from soil for growth. Grow away from light down into soil
                      • Negative phototropism: roots, need nutrients + water from soil for growth. Grow away from light down into soil
          • First, the no. of organelles increase, then choromosomes are copied so cell has 2 copies of its DNA
            • New cells are needed for GROWTH & REPAIR produced by MITOSIS
            • Before cell divides, the DNA forms X-shaped chromosomes. Each 'arm' of a chromosome clones
              • Chromosomes line up in the nucleus & cell fibres pull them apart to opposite ends
                • Membranes form around each sets of chromosomes- nuclei of 2 new cells
                  • Lastly, cytoplasm  divides & you have 2 new cells clone of parent cell- same DNA
          • Gametes have 1 copy of each chromosome so when fertilised, zygote will have full set of 46

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      Sadaf


      This is great!

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