Genetic Modification (3.5)

Question 1

Define restriction enzymes.

Answer 1

A bacteria’s defence mechanism that are used to chop up the invading virus’ DNA. These enzymes always cut DNA at the same base sequence. Scientists have been able to manipulate these enzymes and use them as DNA scissors.

Question 2

What is the polymerase chain reaction?

Answer 2

The PCR is an artificial method of replicating DNA under laboratory conditions. It is used to amplify large quantities of a specific sequence of DNA from an initial minute sample.

Question 3

Describe the stages of the polymerase chain reaction.

Answer 3

A PCR occurs in a thermal cycler. First the DNA sample is collected and it is added to a PCR tube along with primers, nucleotides, Taq polymerase (heat resistant) and a mix buffer. The tube is put into the thermal cycler and temperature variations are used to control the temperature. 1) Denaturing.The DNA sample is heated to separate it into two single strands.2) Annealing.DNA primers are bound to the template.3) Elongation. Taq polymerase binds to the primer and copies the strand.

Question 4

What are applications of the polymerase chain reaction?

Answer 4

Used by the police to identify criminals.Used to check ancient fossils.Used by scientists to check for specific genes.Used to identify viruses eg. COVID-19.Used to identify prenatal genetic disorders.

Question 5

What is gel electrophoresis?

Answer 5

A laboratory technique used to separate and isolate proteins or DNA fragments based on mass / size.

Question 6

Describe the stages of gel electrophoresis.

Answer 6

Agarose gel is made with wells in it. The gel is flooded with a buffer solution that will allow electricity to pass through. The DNA samples are loaded into the wells and the electrodes are turned on. The negative electrode is by the wells and the positive electrode is furtherest away from the DNA. The DNA is attracted to the positive electrode so moves towards it. The smallest pieces move the fastest. To visualise the fragments dye is often added.

Question 7

How can we determine the size of DNA fragments in gel electrophoresis?

Answer 7

The rate at which the fragments move is inversely proportional to their length so their exact size can be calculated.

Question 8

What is an application of gel electrophoresis?

Answer 8

DNA profiling (fingerprinting).

Question 9

What is DNA profiling?

Answer 9

A technique by which individuals can be identified and compared via their respective DNA profiles.

Question 10

Explain satellite DNA.

Answer 10

Within the non-coding regions of an individual’s genome there is satellite DNA. These are long stretches of DNA made up of repeating elements called short tandem repeats (STRs). Individuals have different numbers of repeats so generate different DNA profiles.

Question 11

Describe the procedure of DNA profiling.

Answer 11

A DNA sample is collected and amplified using PCR. Specific restriction enzymes are used to cut satellite DNA into fragments. Fragment length will differ between individuals due to the variable length of their short tandem repeats. The fragments are separated using gel electrophoresis and the resulting profiles are compared.

Question 12

What are the applications of DNA profiling?

Answer 12

Forensics (to match suspects with crime scene evidence)Paternity testing (as children inherit their chromosomes from their parents)Breeding programmes (to test that species are not inbred)

Question 13

How can genetically modified organisms be created?

Answer 13

1) Adding a foreign gene. Produces transgenic organisms.2) Altering an existing gene.3) Deleting or deactivating a gene.*Genes can be transferred between species because the genetic code is universal and the amino acid sequence of the polypeptides translated will code for the same trait.

Question 14

Give an example of genetically modified bacteria in the healthcare industry.

Answer 14

The manufacture of human insulin.

Question 15

Describe the process of modifying bacteria for GMO.

Answer 15

1) The gene of interest is isolating by centrifugation, amplified with PCR and cut using restriction enzymes.2) Plasmids are removed from bacteria. The plasmid is then cut using the same restriction enzyme.3) The cut plasmid and gene of interest are sealed together using the ligase enzyme.4) This recombinant plasmid is inserted back into the bacteria.5) The bacteria reproduces asexually and expresses the desired gene.

Question 16

What are the risk and benefits of genetically modified crops?

Answer 16

Risks:- Can trigger adverse health reactions.- Could reduce biodiversity.- Cross pollination could result in herbicide resistant weeds- Toxins produced by GM crops could negatively affect organisms.Benefits:- Improve human nutrition- Crops can be manufactured that lack common allergens.- Crops can be manufactured to grow in difficult conditions/a wider range of environments.- Larger yield.- Improve food supply in poorer countries.- Longer shelf lives (less spoil).- Economic benefit to farmers.

Question 17

Define gene therapy.

Answer 17

The insertion of genes into an individual’s cells to treat hereditary diseases by replacing defective alleles.

Question 18

What are uses of gene therapy for genetic disorders in humans and ethical concerns?

Answer 18

Gene therapy is used to treat adenosine deaminase deficiency (ADA) which causes severe combined immune deficiency syndrome (SCIDS). However, there are ethical concerns over whether gene therapy can be used to enhance IQ or attractiveness.

Question 19

Define clones

Answer 19

Groups of genetically identical organisms or a group of cells derived from a single original parent cell.

Question 20

How are animals cloned?

Answer 20

Cloning multicellular organisms requires the production of stem cells. Stem cells can be artificially generated using a process called somatic cell nuclear transfer.

Question 21

Describe the process by which animals are cloned.

Answer 21

1) Somatic cells are removed from the adult donor and cultured.2) An unfertilised egg is removed from a female adult donor and its nucleus is removed. This produces an enucleated egg cell. 3) The enucleated egg cell is fused with the donor cell to make a diploid egg cell.4) An electric current stimulates the egg into producing an embryo. 5) The embryo is implanted into the uterus of a surrogate.