Topic 4 - Natural Selection and genetic modification - selective breeding and genetic modification (4.8-4.11)

Question 1

Define genetic engineering

Answer 1

A process in which the genome of an organism is altered in order to achieve desired characteristics.

Question 2

Define selective breeding

Answer 2

When plants or animals with desirable characteristics are chosen to breed together, so that offspring will be produced to inherit these characteristics.

Question 3

Explain selective breeding in plantsq

Answer 3

Plants with desirable features, such as good yield, drought tolerance, and less need for fertilizer, are crossed. Plants grown from these seeds of the crossed plants are selected and crossed with each other. Selection and crossing is repeated until a high yielded variety is produced.

Question 4

Reasons for selectively breeding plants

Answer 4

• disease resistance
• increase yield
• better ability to cope with difficult conditions
• faster growth
• better flavour

Question 5

Describe how a farmer would breed cattle that have a high milk yield

Answer 5

The farmer would choose a cow that produced lots of milk and cross her with a bull whose mother produced a lot of milk. The farmer would then choose the female offspring that produced lots of milk and cross it with another bull whose mother produced a lot of milk. The farmer would repeat this for many generations to increase yield of milk.

Question 6

Tissue culture (plants) process

Answer 6

A sample tissue is taken from the parent plant
This sample tissue is then sterilised
The cells are grown on an agar plate and hormones that cause cell division are added
Hormones that cause roots and stems to form are added to the callus
The individual plants are then planted into the soil.

Question 7

Advantages of using tissue culture

Answer 7

Tests the effect of drugs and other chemicals on cells.
Check for cancer cells in a sample from a patient
Produce important proteins (antibodies)
Produce hundreds of identical plants from just one parent plant
Produce disease free plants.

Question 8

Stages in genetic engineering for making insulin

Answer 8

1) DNA from a human cell is cut into pieces using restriction enzymes. These make staggered cuts across the double stranded DNA, leaving sticky ends at each end.
2) Bacteria cells contain small circles of DNA called plasmids. The same restriction enzymes are used to cut plasmids open, leaving sticky ends with matching sets of unpaired bases.
3) The pieces of DNA containing the insulin gene are mixed with plasmids. The bases in the sticky ends pair up. An enzyme called DNA ligase is added, linking the DNA back into a continuous circle.
4) The plasmids are inserted into bacteria. The bacteria can now be grown in huge fermenters, where they make human insulin.