1.2.1 Chromosomes

• What are chromosomes?

  ● Tightly coiled strands of DNA molecules

  ● Found in nucleus of a cell

  ● Carries a large number of genes

  (section of DNA that codes for a protein)
• How are chromosomes arranged in the nucleus of a body cell?

  In pairs eg. humans - 23 pairs, 46 total
• Why is statement wrong?

  “All organisms have 46 chromosomes.”

  Different species have different numbers of chromosomes.
• Why is this statement wrong?

  “Different cells in the body have different genes / chromosomes / DNA.”

  All cells in the body originate from a fertilised egg cell. This divides

  by mitosis to form all the genetically identical cells of the body.