DNA

• What is DNA made of


  Repeating units made of nucleotides
• What type of backbone does DNA have

  Sugar + phosphate
• What formation does DNA have


  Double helix
• What is a chromosome


  Long coiled up molecules of DNA
• Define genome


  All of the organism's DNA
• What do genes code for 


  Specific protein
• What is DNA (6 marker) 


  • DNA is made up of chromosomes
  • In a double helix
  • Made up of repeating nucleotides
  • Each nucleotide has a sugar phosphate backbone
  • Including bases of A + T & C + G
  • Found in the nucleus
• Why do we add detergent 


  Breaks down cell membrane - releases DNA
• Why do we add salt 


  So DNA sticks together
• Why do we add ice cold ethanol


  DNA is insoluble so in cold alcohol -> forces it out of solution into precipitate
• Describe the DNA extraction practical 


  • Mash up fruit using pestle + mortar
  • Put fruit into beaker containing salt + detergent solution
  • Mix using spatula
  • Filter mixture to remove froth + insoluble bits
  • Gently add ice cold ethanol to filtrate
  • Stringy white precipitate (DNA) will form + collect using glass rod
• describe + explain the steps of meiosis

  • Parent cell
  • Before cell division, DNA duplicates
  • Chromosomes line up in pairs (1 from each parent)
  • Pairs pulled apart so each new cell has 1 copy of each chromosome (genetic variation)
  • 2nd division -> chromosomes line up again + arms of chromosomes are pulled apart into chromatids
  • 4 haploid daughter cells
• what's mitosis

  • making copies + dividing cells to produce twin daughter cells
  • genetically identical diploid cells
• how do you work out the number of cells

  • 2^n
  • n= now many times it's been divided
• why is mitosis useful

  • repairing damaged cells by replacing them or growing cells
  • asexual reproduction
• list stages of mitosis + explain each step

  • interphase = copy of DNA
  • prophase = membrane of nucleus breaks down so chromosomes now in cytoplasm + chromosomes condense
  • metaphase = lines up in centre of cell
  • anaphase = spindle fibres pull them to opposite sides of cell
  • telephone = membrane forms around them
  • cytokines = divides into 2 new cells