Gene technologies

Question 1

Describe the process of genetic engineering

Answer 1

1) A useful gene is cut from the DNA of one organism using an enzyme called a restriction enzyme. This enzyme breaks bonds between nucleotides.

2) Restriction enzymes cut the DNA in a staggered way leaving short sections of single-stranded DNA at each end of the gene (sticky ends)

3) The bacterial plasmid DNA is cut open using the same restriction enzyme. The cut ends of the plasmid also have sticky ends.

The reason for using the same restriction enzyme is so that the sticky ends on the plasmid will have a short sequence of bases that are complementary to those on the ends of the useful gene.

4) The useful gene and the plasmid DNA are mixed and the gene is inserted into the plasmid. Hydrogen bonds form between the complementary bases in the sticky ends of the plasmid and the useful gene.

5) The enzyme DNA ligase is used to join the plasmid DNA and the useful gene together. The ligase joins the end nucleotides of the useful gene to the end nucleotides of the plasmid = recombinant plasmid

6) The recombinant plasmid is then inserted into a bacterial cell. The plasmid acts as a vector, carrying the gene into the bacterial cell.

7) The bacterial cell is now a GMO. It can be cultured by cloning and the cell can use the gene that has been inserted into it to make a protein.

Question 2

Why are Agrobacterium tumefaciens bacteria used to create GM plants

Answer 2

These bacteria have a plasmid called a Ti plasmid. When the bacteria infect plants, the Ti plasmid is able to enter plant cells and a portion of the Ti plasmid inserts itself into the plant genome.

Question 3

Describe fertilisation and the different types of cells that derives from this

Answer 3

Two gamete cells fuse together at fertilisation to produce a fertilised egg cell called the zygote.

The zygote will then divide by mitosis to produce two daughter cells. These cells will also divide by mitosis to produce more cells and a new life starts to develop.

Question 4

Describe selective breeding

Answer 4

Animals with desirable characteristics are selected for breeding.

These animals are bred together.

The animals with the most desirable characteristics are selected from the offspring.

These offspring animals are then bred together.

This cycle is repeated over many generations.

Over time the desirable characteristic starts to increase in the population, e.g. animals which have a higher and higher growth rate.