1. What do chromosomes carry, and how many copies of each chromosome are found in a human body cell ?
Answer
Chromosomes carry a large numbers of genes. Each cell contains two copies of each chromosome.
2. Besides development, what is another role of mitosis in multicellular organisms ?
Answer
Mitosis repairs damaged tissues by replacing old or injured cells with genetically identical new cells.
3. Give two advantages of producing plant clones using stem cells from meristem tissue.
Answer
Clones of plants can be produced quickly and economically.
4. Give one other change that happens in a cell before it divides that is not related to its genetic material.
Answer
The cell grows, because the number of sub–cellular structures increases.
5. The figure below shows some cells at different stages of the cell cycle. Which cell is not dividing by mitosis? What is happening in cell B and E ?
Answer
Cell D is not dividing by mitosis. One set of chromosomes is pulled to each end of the cell B and the nucleus divides. The cytoplasm and cell membrane of cell E have divided to form two identical (daughter) cells.
6. Describe the main difference between stem cells from embryos and stem cells from adult bone marrow.
Answer
Stem cells from human embryos can be cloned and made to differentiate into most different types of human cells. Stem cells from adult bone marrow can form many types of cells including blood cells.
7. Name two conditions that could be treated with stem cells.
Answer
Diabetes and paralysis.
8. A patient with leukaemia can be treated using stem cells taken from their own bone marrow. What are some advantages and disadvantages of using these stem cells ?
Answer
Using stem cells from the patient offers several advantages: it involves no ethical concerns due to informed consent, ensures patient safety, and relies on a reliable technique that has been tried and tested over many years.
Using stem cells from the patient has disadvantages, including a risk of infection from surgery and potential pain that may discourage patients.