Topic 4.4 Genetic engineering and biotechnology

Question 1

4.4.1 Outline the use of polymerase chain reaction (PCR) to copy and amplify minute quantities of DNA.

Answer 1

1. Sample is added to a test tube with DNA polymerase from a thermophilic bacteria Thermus aquaticus
   
   • High temp allows reaction to hapen quicky
   • Polymerase from thermophilic bacteria used as it will work even in high temps
2. DNA primers are added and temperature is cycled between 95°C → 53°C → 73°C to make multiple copies
3. Can make _~ million copies in an hour

Question 2

4.4.2 State that, in gel electrophoresis, fragments of DNA move in an _______ field and are separated according to their ____.

Answer 2

In gel electrophoresis, fragments of DNA move in an electric field and are separated according to their size.

Question 3

4.4.3 State that gel electrophoresis of DNA is used in ___ _________.

Answer 3

Gel electrophoresis of DNA is used in DNA profiling.

Question 4

4.4.4 Describe the application of DNA profiling to determine paternity and also in forensic investigations.

Answer 4

• DNA fingerprinting
  
  • Non-coding sections of DNA are used
    
    • contain regions called hypervariable regions, which have repeating nucleotide sequences
  • DNA is chopped into pieces by enzymes which cut between specific sequences
  • Since everyone has diff. # of these sequences, everyone’s DNA gets sliced slightly differently
• Gel electrophoresis
  
  • method of separating chunks of DNA
  • spliced DNA is put in a gel that has an electric current run through it
  • DNA fragments move through gel, but at different speeds depending on their polarity & size (charged & small = faster)
• ​DNA profiling used in paternity testing…
  
  • blood test can only rule out paternity (baby is O, “Dad” is AB)
• and forensic investigations
  
  • to identify remains
    
    • e.g. ID blood, semen, hair, etc. from crime scene

Question 5

4.4.5 Analyse DNA profiles to draw conclusions about paternity or forensic investigations.

Answer 5

Paternity testing

• ignore lined-up DNA fragments between mother and child
• line up child’s DNA with male’s DNA; whichever male matches child the most is the father

Forensic investigation

• line up evidence’s DNA fragments with suspects’ DNA fragments; whichever suspect matches is “guilty”

Question 6

4.4.6 Outline three outcomes of the sequencing of the complete human genome.

Answer 6

1. Can help find location of genes that cause genetic conditions
2. Can find location of genes that produce things we need and get them made in labs
3. Production of new medications
4. Details about human ancestry and migration patterns can be determined
5. Pharmaceutical companies have patented genes

Question 7

4.4.7 State that, when genes are transferred between species, the amino acid sequence of polypeptides translated from them is ________ because the genetic code is universal.

Answer 7

When genes are transferred between species, the amino acid sequence of polypeptides translated from them is unchanged because the genetic code is universal.

Question 8

4.4.8 Outline a basic technique used for gene transfer involving plasmids, a host cell (bacterium, yeast or other cell), restriction enzymes (endonucleases) and DNA ligase.

Answer 8

1. Genetic probe used to locate specific gene on the donor cell
2. Restriction endonucleases is used to cut desired DNA from donor genome, isolating it
3. Same endonucleases used to cut open a plasmid from E. Coli (will be used as a vector)
4. Donor DNA is modified in a highly selective way, involving combination of plasmid and donor DNA and DNA ligase binding the ends together
5. Transfer the plasmid into new bacterial host cells in such a way that the gene will be expressed strongly enough to be of practical use
6. plasmid replicates in bacterial host and begins making its own product

Question 9

4.4.9 State two examples of the current uses of genetically modified crops or animals.

Answer 9

• Herbicide resistance in crop plants
• Salt tolerance in tomato plants
• Human insulin production by bacteria
• Factor IX (clotting factor) in sheep milk
• Synthesis of beta carotene in rice plants (Golden Rice)
• Alpha-1-antitrypsin (helps protect lungs from damage during infection) in sheep milk

Question 10

4.4.10 Discuss the potential benefits and possible harmful effects of one example of genetic modification.

Answer 10

Maize introduced with a bacterial gene encoding a protein called Bt toxin.

Benefits

• Allows for introduction of a characteristic that wasn’t present within the gene pool (selective breeding could not have produced desired phenotype)
• Results in higher crop yield
• Requires less land for comparable yield
• Less use of chemical pesticides, reducing the economic cost of farming
• Can now grow in previously unsuitable regions (reduces need for deforestation)

Consequences

• Could have currently unknown harmful effects (e.g. toxin may cause allergic reactions in a percentage of the population)
• Accidental release of transgenic organism into the environment may result in competition with native plant species
• Possibility of cross pollination (if gene crosses the species barrier and is introduced to weeds, may have a hard time controlling weed growth)
• Insects unharmful to maize plant could be killed due to maize pollen containing toxin blowing onto nearby plants

Question 11

4.4.11 Define clone.

Answer 11

Clone: group of genetically identical organisms or a group of cells derived from a single parent

Question 12

4.4.12 Outline a technique for cloning using differentiated animal cells.

Answer 12

Somatic Cell Nuclear Transfer (SCNT) is a method of reproductive cloning using differentiated animal cells.

• A female animal (e.g. sheep) is treated with hormones (such as FSH) to stimulate the development of eggs
• The nucleus from an egg cell is removed, thereby removing the genetic information from the cell
• The egg cell is fused with the nucleus from a somatic (body) cell of another sheep, making the egg cell diploid
• An electric shock is delivered to stimulate the egg to divide, and once this process has begun the egg is implanted into the uterus of a surrogate
• The developing embryo will have the same genetic material as the sheep that contributed the diploid nucleus, and thus be a clone

Question 13

4.4.13 Discuss the ethical issues of therapeutic cloning in humans.

Answer 13

• Therapeutic cloning: creation of an embryo to supply embryonic stem cells for medical use
  
  • e.g. skin grafts, grow new organs

Support

• May be used to cure serious diseases or disabilities with cell therapy (replacing bad cells with good ones)
• Stem cell research may pave the way for future discoveries and beneficial technologies that would not have occurred if their use had been banned
• Stem cells can be taken from embryos that have stopped developing and would have died anyway (e.g. abortions)
• Cells are taken at a stage when the embryo has no nervous system and can arguably feel no pain

Opposition

• Involves the creation and destruction of human embryos (at what point do we afford the right to life?)
• Embryonic stem cells are capable of continued division and may develop into cancerous cells and cause tumors
• More embryos are generally produced than are needed, so excess embryos are killed
• With additional cost and effort, alternative technologies may fulfill similar roles (e.g. nuclear reprogramming of differentiated cell lines)