5.10- 5.16 selective breeding, GM

What is selective breeding?

When humans choose organisms to breed in order to produce offspring with a certain desirable characteristic

Process of selective breeding

1. Parents with desired characteristics are chosen

2. They are bred together

3. Offspring with the desired characteristics are bred together

4. Process is repeated many times until all offspring have desired characteristic

Problems with selective breeding

• Can cause inbreeding - breeding those with similar characteristics means you are likely breeding closely related organisms

  • Results in reduction of gene pool as number of different alleles reduce (most have same)

  • If environment changes/new disease, species can become extinct (Few have survival advantage)

  • Small gene pool causes greater chance of genetic defects in offspring

What is genetic engineering?

Modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic

What are restriction enzymes used for?

To cut the required gene out of the DNA - results in pieces of DNA with sticky ends

What are ligase enzymes

Enzymes that are used to join pieces of DNA together

What are sticky ends

Short sections of single-stranded DNA which pair together with another that contains complementary bases

Process of genetic modification

1. The gene is cut out using restriction enzyme leading sticky ends

2. A bacterial plasmid (transfer DNA into bacteria or yeast) or virus (transfer DNA into human cells or bacteria) is cut using the same restriction enzyme to create sticky ends that match the gene (acts as vectors)

3. The sticky ends from the plasmid and the genes are joined together by ligase enzymes creating a recombinant plasmid

4. The recombinant plasmid is inserted into host bacterium and one allowed to multiply and express new gene

Process of producing insulin from genetically modifying bacteria

• gene for insulin production located within human chromosome which restriction enzymes are used to isolate/cut out leaving it with sticky ends

• A bacterial plasmid is cut by the same restriction enzyme leaving it with corresponding sticky ends

• The plasmid and the isolated human insulin gene are joined together by ligase enzyme

• The recombinant plasmid is inserted into a bacterial cell

• When the bacteria reproduce, the plasmids are copied as well and so a recombinant plasmid can quickly be spread and will express the human insulin gene, making human insulin protein

• It can be placed in a fermenter to reproduce quickly in controlled conditions to make large amounts of human protein

What is manufacturing insulin used for?

For medical use to treat diabetes

What are crops genetically modified to be?

To be resistant to insects and herbicides, increasing yield

To produce additional vitamins

Advantages of GM crops

• reduced use of chemicals (pesticides) - better for environment

• Cheaper/less time consuming

• Increased yields

Disadvantages of GM crops

• increased costs of seeds

• Increased dependency on certain chemicals

• Risk of inserted genes being transferred to wild plants by pollination

• Reduced biodiversity

What is transgenic

Transfer of genetic material from one species to a different species