Biotechnology: Recombinant DNA

Question 1

Recombinant DNA

Answer 1

DNA composed of one or more genes from two different organised

Question 2

Transgenic Organism

Answer 2

An organism that contains genetic material into which DNA from an unrelated organism has been artificially introduced in order to meet a specific purpose

Question 3

Restriction Enzymes

Answer 3

Enzymes that cut DNA molecules into segments called restriction fragments at known sequences, called restriction sites. Each enzyme recognises a specific sequence of 4-8 nucleotide base pairs, binding to the restriction site and cutting the double strand.

Question 4

Restriction Fragments

Answer 4

A fragment of DNA molecule that has been cut by a restriction enzyme

Question 5

Restriction Sites

Answer 5

The specific sequence of DNA that a restriction enzyme binds to in order to cut it

Question 6

Sticky Ends

Answer 6

Restriction enzyme leaves overhanging steps which leave some nucleotides exposed

Question 7

Blunt Ends

Answer 7

Restriction enzyme cuts at the same position on each strand of DNA and there are no overhanging strands

Question 8

DNA Ligase

Answer 8

Enzyme able to join or recombine separate pieces of DNA by forming a phosphodiester bond between them. DNA ligase can easily combine fragments with complementary sticky ends, while those with blunt ends are less stable.

Question 9

Vector

Answer 9

A segment of DNA capable of replicating on its own and transporting foreign genetic material into another cell

Question 10

Plasmid

Answer 10

Circular double stranded units of cytoplasmic DNA capable of replicating within a cell independently of chromosomal DNA. DNA fragments can be inserted into a plasmid, which can then be introduced into a bacterium for cloning.

Question 11

Step 1: Cut Gene of Interest

Answer 11

Isolate the gene of interest in the donor organism and cut the sequence out using a restriction enzyme, making sure that the resulting restriction fragment has sticky ends

Question 12

Step 2: Cut Plasmid from Bacterial Cell

Answer 12

Isolate a plasmid from a bacterial cell and cut it with the same restriction enzyme as used on the gene of interest

Question 13

Step 3: DNA Ligase

Answer 13

Splice the DNA into the plasmid. Hydrogen bonds draw the complementary bases of the plasmid and the restriction fragment together, and DNA ligase binds the two together at the sticky ends, creating a recombinant plasmid

Question 14

Step 4: Gene cloning

Answer 14

Place the recombinant plasmid into bacteria for gene cloning. Bacteria replicate the plasmid via binary fission.

Question 15

Step 5: Creating transgenic organism

Answer 15

The bacterial vector is then inserted into a host organism by a gene gun or other method to create a transgenic organism.

Question 16

Example: Hornless Holstein Cows

Answer 16

• Holstein cows are dairy cows that naturally grow horns
• They are dangerous to other cows and farmers, so must be removed
• Angus (beef) cows have a naturally occurring mutation that makes them not grow horns
• Breeding an Angus with a Holstein would result in a cow that wouldn’t be suited for either beef or dairy
• Researchers at University of California-Davis introduced hornless gene from Angus cows into the horn gene of Holstein cows, leaving the milk-producing gene unaffected
• Produced two hornless Holstein bulls with homozygous dominant hornless alleles