B5 - Growth and development

B5 - Growth and development

1. PRODUCING NEW CELLS

   • THE CELL CYCLE
     • Cells for growth and repair
     • STAGE 1 - CELL GROWTH
       • Organelles double
       • DNA replicates 46-92 chromosomes
         • Base pairs
           • A-T
           • C-G
       • STAGE 2 - MITOSIS
         • 1. Nuclear membrane bursts
         • 2. Chromosomes pair up
         • 3. Chromosomes line up in the centre of the cell
         • 4. Chromosomes are pulled apart
         • 5. 46 chromosomes to one side of the cell & 46 to the other side. Nuclear membranes form around the chromosomes.
         • 6. The cell membrane splits the cell into two daughter cells with identical genetic information.
   • MEIOSIS
     • Produces 4 genetically different cells
     • Produces gametes with 23 chromosomes each
       • Sex cells
         • Male
           • Sperm
         • Female
           • Ovum
     • 1. Chromosomes replicate
     • 2. Chromosomes pair up and some genetic information swaps
     • 3. Chromosomes are pulled apart 46 to each side of the cell
     • 4. The cell divides into two daughter cells
     • 5. Chromosomes separate again 23 to each side of each of the two new cells
     • 6. A new nuclear membrane forms around each set of 23 chromosomes
     • 7. The cell membrane splits the two cells in half again, creating 4 genetically different daughter cells.

2. GENES

   • Switches
     • All genes are switched on in Embryonic stem cells
       • As all genes are switched on all types of proteins can be made and the cell can become any type of cell
     • In specialised cells only genes that are needed by the cell are switched on
       • Only certain proteins are made by the cell, depending on which genes are switched on
   • Genes are sections of a chromosome
     • Chromosomes are made of DNA
       • Chromosomes are found in the nucleus of a cell
   • Genes are the instruction for making proteins
     • Proteins are long chains of Amino acids
     • PROTEIN SYNTHESIS
       • The DNA strand is too big to leave the nucleus of the cell
         • The DNA strand unravels, but only the section (gene) that holds the code for making the required protein
           • messenger RNA (mRNA) bases pair up to the exposed bases of the DNA strand A-U and C-G
             • The mRNA strand detaches itself and moves out of the nucleus
               • The Ribosomes in the cytoplasm read the bases of the mRNA in 3s (triplet code)
                 • Each triplet codes for one Amino acid
                   • The ribosomes links the Amino acids in order to form the correct protein

3. PLANTS

   • CLONES
     • Taken from cuttings
       • Dip in rooting powder that contains Auxins
         • Roots grow and genetically identical plant can grow
   • PHOTOTROPISM
     • Makes plants grow towards the light
       • Increases amount of glucose produced by photosynthesis as rate of photosynthesis increases
         • This increases plants chance of survival
     • Auxins
       • Plant hormone
         • Moves away from light
         • Elongates cells that is comes into contact with
           • If the light is above the plant Auxon moves down the shoot making the cells below the tip elongate and the shoot grown tall and straight
           • If the light comes from the left then Auxin moves to the right hand side of the plant. The cells on the right elongate and the shoot bends to the left
           • If the lights comes from the right then Auxin moves to the left hand side of the plant. The cells on the left elongate and the shoot bends towards the right
         • Found in shoot tips and root tips
   • MERISTEMS
     • Unspecialised cells in plants
       • Found in shot tip, root tip, stem and buds
     • Reproduce mitotically
       • Produced two daughter cells
         • one remains as a meristem and the other becomes specialised
   • CELLS, TISSUES and ORGANS
     • Cells
       • Palisade cells
         • Contain chloroplasts responsible for photosynthesis
       • Root hair cell
     • ORGANS
       • Roots
       • Leaves
       • Flowers
       • Stem
     • Tissues
       • Xylem
         • Carries water around the plant
       • Phloem
         • Carries the products of photosynthesis around the plant

4. MULTI_CELLULAR ORGANISMS

   • CELLS
     • Unspecialised
       • Embryonic stem cells
         • Found only up to 8 cell stage
           • Can become any type of cell
       • Adult stem cells
         • Found in everyone
           • Are limited in the type of cell they can become
   • TISSUES
     • A group of the same cells
       • e.g. lots of muscle cells together produce muscle tissue
   • ORGANS
     • A group of different tissues working together to do a job
       • e.g. muscle tissue, blood vessel tissue etc. create the heart