Cloning PAPER 2

Question 1

What is micropropagation (tissue culture)?

Answer 1

1) plant with desirable characteristics is selected to be cloned. Small pieces (explants) are taken from the tip of the stems + side shoots
2) The explants are sterilised to kill any microorganisms
3) The explants are then grown in vitro - they’re placed in a Petri dish containing a nutrient medium. The medium has all the nutrients and growth hormones needed for the plant
4) Cells in explants divide and grow into a small plant
5) The explants are taken out of the medium, planted in soil and put into glasshouses - they’ll develop into plants that are genetically identical to the original plant

Question 2

How can micropropagation be used to produce commercial quantities of genetically identical plants

Answer 2

• if large quantities of plants are required (to sell), further explants can be taken from these small plants
• this can be repeated until enough small plants are produced
• the small plants are taken out of the medium, planted in soil and put into glasshouse
• they’ll develop into genetically identical plants

Question 3

How is a mammal cloned? (Eg. Dolly the sheep)

Answer 3

(Example of dolly the sheep)
- the nucleus of a sheep’s egg cell was removed, creating an enucleated cell (cell without nucleus)
- a diploid cell was inserted in its place - nucleus from another body cell of a different sheep
- the cell is stimulated (by an electric shock) so that it starts to divide by mitosis like a normal fertilised egg
- the dividing cell is planted into the uterus of the surrogate mother to develop until it is ready for birth
- result is a sheep (dolly), a clone of the sheep the body cell came from

Question 4

How do cloned transgenic animals produce human proteins

Answer 4

• cows and sheep make proteins naturally in their milk
• by transferring the human genes into the cells of these animals could get them to produce useful human proteins in their milk

Question 5

How can human proteins from cloned transgenic animals be used?

Answer 5

• they can produce human antibodies that can be used in therapy for illnesses like arthritis, some types of cancer and multiple sclerosis
• transgenic chickens have been engineered to produce human proteins in egg white
• transgenic animals can be cloned so that useful characteristics are passed - this doesn’t always happen with normal breeding