Unit 2 - Topic 12 - Applied Genetics

Question 1

What is cystic fibrosis?

Answer 1

Cystic fibrosis is a recessive inherited genetic condition, (i.e. not sex linked).

Causes problems with breathing and food digestion.

Question 2

Definition: Mutation

What are the two different types of mutation?

Answer 2

A random genetic change to the structure or number of chromosomes.

• There are two types of mutations:
  1. Gene mutation
  2. Chromosome mutation

Question 3

Give an example of a genetic condition caused by a chromosome mutation.

Answer 3

Down Syndrome

Question 4

Give an example of a genetic condition caused by a gene mutation.

Answer 4

Haemophilia

Question 5

Give an example of a dominant inherited genetic condition.

Answer 5

Huntington’s Disease

Question 6

Mutations can be triggered by …

Answer 6

Environmental factors/causes.

Question 7

Give some examples of environmental factors/causes.

Answer 7

UV radiation
Chemicals (carcinogens)
Viruses

Question 8

What is Down syndrome caused by?

Answer 8

Down syndrome is caused by a chromosome mutation. This condition is caused by an error in the formation of gametes. Occasionally gametes are formed with 24 chromosomes. If the affective gamete is fertilised, the new individual will have 47 chromosomes in all of his or her cells instead of the normal 46.

The extra chromosome is present at position 21.

Question 9

What is an amniocentesis test?

Answer 9

Cells are taken from the amniotic fluid surrounding the baby in the womb. The foetal cells are then cultured and allowed to multiply in laboratory conditions. The chromosomes in the cells are then analysed to test for genetic conditions.

Question 10

What is genetic screening?

Answer 10

Genetic screening may be used to reduce the incidence of diseases or conditions caused by problems with our chromosomes or genes. It involves testing people for the presence of a particular allele or genetic condition.

Question 11

What are the ethical issues of genetic screening?

Answer 11

• The ethics of abortion for medical reasons.
• Is there an acceptable risk associated with genetic screening? For example, amniocentesis for Down Syndrome screening has a small risk of miscarriage.
• Should parents be allowed free choice whether to screen or not?
• Should you be allowed to screen for the sex of a child? What if it is not the sex you want?
• Costs of screening compared to the costs of treating individuals with a genetic condition - should cost be a factor?
• Should genetic screening be extended to more than just serious genetic conditions? What if it can predict life expectancy?
• The dilemma for carriers of genetic conditions in becoming pregnant.

Question 12

What is genetic engineering?

Answer 12

Genetic engineering involves taking a piece of DNA, usually a gene, from one organism (the donor) and adding it to the genetic material of another organism (the recipient), thereby altering the organisms genetic code.

Question 13

Commonly, DNA that codes for the desired product is incorporated into the DNA of bacteria. Why is this?

Answer 13

This is because bacterial DNA is easily manipulated and also because bacteria reproduce so rapidly that large numbers can quickly be produced with the new gene.

Question 14

Give an example of a product produced by genetic engineering.

Answer 14

Insulin

Question 15

Describe the steps and techniques needed to produce human insulin via genetic engineering.

Answer 15

1. The human insulin gene is removed from the human DNA with the use of a restriction endonuclease enzyme (such as Eco R1) to isolate the desired gene and expose ‘sticky ends’.
2. A plasmid is then removed from the bacterial cell and is exposed to the same restriction endonuclease enzyme (such as Eco R1) to cut open the plasmid and expose the same ‘sticky ends’.
3. The human insulin gene is then inserted into the altered plasmid due to complimentary sticky ends (supported by the base pairing rules, e.g. A to T, C to G). The two pieces of DNA are joined together using DNA ligase.
4. The recombinant plasmid is then placed back inside the bacteria, and the bacteria is placed inside a biodigester or fermenter with optimal conditions to maximise bacterial growth.
5. The bacteria then reproduces by mitosis (binary fission), producing large amounts of insulin in a short amount of time.
6. The insulin product is then extracted, purified and packaged (down streaming).

Question 16

What is insulin?

Answer 16

A hormone consisting of proteins, made from amino acids, which converts glucose to glycogen to regulate blood-sugar levels.

Question 17

What condition does insulin treat?

Answer 17

Diabetes

Question 18

What are the problems with obtaining insulin from natural sources?

Answer 18

1. Insulin can be obtained from animals such as dogs, cattle and pigs, but it takes a large amount of pancreas material to produce minute quantities of insulin.
2. The insulin obtained is not identical to the human insulin.
3. Extraction of the hormone is very difficult.

Question 19

What are the advantages of using insulin from genetically modified organisms?

Answer 19

1. GE insulin is identical to human insulin and so diabetics who use it do not suffer adverse reactions when using it, unlike the other forms of insulin obtained from animals.
2. The quantities produced are much greater and have overcome the shortage of insulin.
3. Production costs are much lower, and so cheaper supplies can be produced.
4. Objection on ethical or religious grounds, to using animals, are overcome.