paper 1 biology

• ...Finish the statement...

  
  

  DNA exists in a cell's nucleus within structures called ... ?

  Chromosomes
• ...Finish the statement...

  
  

  Each section of a chromosome that contains the code for the production of a particular protein is called a ... ?

  Gene
• What is mitosis?


  A type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus. Used for ordinary tissue growth and repair.
• Describe the process of mitosis...

  Chromosomes replicate so there are 2 copies of it.

  
  

  It then condenses.

  
  

  The chromosomes line up at the centre of the cell and cell fibres pull them apart.

  
  

  The two arms of each chromosome go to opposite ends of the cell.

  
  

  Membranes form around each of the sets of chromosomes.

  
  

  These become the nuclei of the two new cells.

  
  

  Lastly, the cytoplasm and cell membrane divide.

  
  

  The cell has now produced two new daughter cells, which contain the same DNA as the parent cell.

  
• Each human body cell contains how many PAIRS of chromosomes?

  23
• What are the 23rd pair of chromosomes?

  Sex chromosomes
• What does having XX sex chromosomes mean?


  This person has female sex chromosomes
• What does having XY sex chromosomes mean?

  This person has male sex chromosomes
• Describe the cell cycle...

  1) Growth

  2) Synthesis

  3) Growth and checking for errors

  4) Mitosis

  5) 2 cells are formed as the cytoplasm separates

  6) Temporary cell resting period

  
  

  **REPEAT**

  
• How do you measure the length of time in a phase?

  (Observed number of cell at that stage/ total number of cell observed) * total length of cell cycle
• What are stem cells?

  Cells that have not undergone differentiation.

  
  

  A cell which has not yet become specialised is called undifferentiated.
• Give an example of human stem cells...


  - The early stages of an embryo (embryonic stem cells)

  
  

  - Adult stem cells are found in small numbers in certain areas of the body including the marrow, liver blood and more
• Can embryonic stem cells or adult stem cells become any kind of cell?

  Embryonic

  
  

  Adult stem cells can differentiate only into a selection of related cells
• What are meristems?


  The regions in plants to which growth happens, they can differentiate to produce all types of plant cells at any time during the life of the plant.

  
  

  They are stem cells
• Where can the main plant meristems be found?

  Tip of roots and shoots.
• Give an example of a disease in which stem cells might help with

  Diabetes or paralysis
• Why in therapeutic cloning do we produce embryos with the same genes as the patient?

  Stem cells from the embryo are not rejected by the patient's body so they may be used for medical treatment.
• What are the risk of stem cells?

  Transfer of viral infection, and some people have ethical or religious objections.
• What are the uses of producing clone plants?

  • Rare species can be cloned to protect from extinction.

  
  

  • Crop plants with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers.