19.2 - Gene tech applied to medicine

Question 1

What is recombinant DNA?

Answer 1

• DNA that has been altered

- by introducing nucleotides sequences from another source

Question 2

How are recombinant proteins formed?

Answer 2

• recombinant DNA has been used to produce recombinant proteins
• produced using eukaryotic cells (yeast) as prokaryotic cells will carry out post-translational modification (due to presence of Golgi Apparatus)
• RP are manipulated forms of the original protein

Question 3

State the advantages of using GE organisms to produce RP

Answer 3

> cost-effective to produce in large volumes
more simple than prokaryotic cells
faster in producing many proteins
reliable supply available
proteins engineered are identical to human proteins
- have modifications that are beneficial
no moral, ethical or religious concerns against usuing cow/ pork produced proteins

Question 4

Describe and explain how recombinant insulins are produced

Answer 4

> bacteria plasmids are modified to include human insulin gene
- restriction endonucleases are used to cut open plasmids
- DNA ligase used to splice plasmid and human DNA together
recombinant plasmids are then inserted into Escherichia coli by transformation (bath of Ca+/ electric shock)
transgenic bacteria isidentified by markers and are isolated, purified and placed in fermenters providing optimal conditions
transgenic bacteria multiply by binary fission and express the human protein insulin
- insulin expressed is extracted and purified

Question 5

State the advantages of using recombinant insulin

Answer 5

> identical to human insulin
- unless modified (act faster)
reliable supply available
- meet demand
- no need to depend on availability of meat stock
fewer ethical, moral or religious concerns
- the proteins are not extracted from cows or pigs
fewer rejection problems/ side effects or allergic reactions
cheaper to produce in large volumes
useful for people who have animal insulin tolerance

Question 6

Describe how recombinant Factor VIII produced and used

Answer 6

• Factor VIII is a blood - clotting protein
• kidney and ovary hamster cells have been genetically modified to produce factor VIII
• once modified, the recombinant cells are placed into a fermenter and cultured
• due to optimal conditions in fermenter, hamster cells constantly express factor VIII
• the protein is then extracted and purified to be used as an injectable treatment for haemophilia

Question 7

State the advantages of using recombinant Factor VIII

Answer 7

> fewer ethical, moral or religious concerns
- proteins are not extracted from human blood
less risk of transmitting infection/ diseases (HIV)
greater production rate

Question 8

Explain what is ADA and how it is produced and used

Answer 8

• adenosine deaminase (ADA) is an enzyme used to treat the inherited condition called Adenosine Deaminase Deficiency which causes Severe Combined Immunodeficiency (SCID)
• immune system is damaged
• larva of the cabbage looper moth has been genetically modified (using a virus vector) to produce the enzyme adenosine deaminase
• it can be used as a treatment whilst patient wait for gene therapy/ or when gene therapy is not possible

Question 9

State the advantages of using recombinant adenosine deaminase

Answer 9

> fewer ethical, moral or religious concerns
- proteins are not extracted from cows
less risk of transmitting infection/ disease
- from cows
more reliable of production of the enzyme
faster to produce many proteins

Question 10

What is genetic screening, and what is it used for?

Answer 10

• the testing of an embryo, fetus or adult to analyse the DNA
• help identify if individuals carry an allele at a gene locus for a particular disease

Question 11

How are the sample of DNA obtained to be analysed by genetic screening?

Answer 11

> taking tissues from adults/ embryos produced by in-vitro fertilisation
chorionic villus sampling/ amniocentesis of embryos and fetuses in the uterus

Question 12

State the uses of genetic counsellors

Answer 12

> can be seen before or after screening has occured
to discuss:
- the chances of the couple having a child with the certain disease
- termination of pregnancy
- therapeutic treatments possible for the child
- financial implications of having the child
- effect on existing siblings
- ethical issues

Question 13

Describe how breast cancer (BRCA1 and BRCA2) occurs

Answer 13

• BRCA1 and BRCA2 are genes that produce tumour suppressor proteins
• the genes play an important role in regulating cell growth
• when faulty alleles of these particular genes exist, it increases the risk of an individual developing breast/ ovarian cancers
• BRCA1 and BRCA2 alleles can be inherited from either parent

Question 14

State the advantages of genetic screening for BRCA1 and BRCA2

Answer 14

> person may decide to take preventative measures
- e.g: having elective mastectomy to reduce the risk of developing cancer
screening for breast cancer may begin from an earlier age and more frequently
- individual (if female) will have more frequent clinical examination of the ovaries
enables person to participate in research and clinical trials

Question 15

What is Huntington’s disease

Answer 15

• A progressive and inherited disease that affects the brain
• include uncontrolled movements, lower cognitive (thinking) ability
• no cure, only treatments available to alleviate symptoms
• it is an autosomal dominant disease
• therefore, if the person has an allele for Huntington’s they will get the disease

Question 16

State the advantages of genetic screening for Huntington’s

Answer 16

> people to plan for the future
- how they will live and be cared for
couples to make informed reproductive decisions
- risk that children may inherit the disease is 50%
- people participate in research and clinical trials

Question 17

Describe cystic fibrosis

Answer 17

• an autosomal recessive genetic disorder
• caused by a mutation of a gene that codes for a transported protein, called CFTR
• a progressive disease that causes mucus in various organs (lungs, pancreas) to become thick and sticky
• due to faulty CFTR protein that no longer transports chloride ions across the cell plasma membrane
• therefore, water does not move by osmosis across the membrane wither
• presence of water would make mucus thinner, enabling cilia to remove it
• no cure for cystic fibrosis, only treatments to alleviate symptoms
• common death is bacterial infection in the lungs

Question 18

State the advantages of genetic screening for cystic fibrosis

Answer 18

> enables couple to make informed reproductive decisions
- both may be carriers and therefore not display any symptoms
people can participate in research and clinical trials

Question 19

State the common advantage in genetic screening

Answer 19

• allows couple to make informed reproductive decisions

- people can participate in research and clinical trials

Question 20

What is gene therapy?

Answer 20

• involves using various mechanisms to alter a person’s genetical material
• able to replace a faulty gene, inactivate a faulty gene, or insert a new gene
• to treat, cure diseases

Question 21

Why, effects of changing the somatic cells are short-lived?

Answer 21

• somatic changes in genetic material are targeted to specific cells
• will not be inherited by future generations
• as somatic gene therapy does not target the gametes
• gene therapy cells is not permanent, whereas in germ cells (gametes) it is permanent

Question 22

State and describe the two types of somatic gene therapy

Answer 22

> ex vivo
- new gene is inserted via a virus vector into the cell outside the body
- blood or bone marrow cells are extracted and exposed to the virus which inserts the gene into the cells
- the cells are grown in the laboratory and returned to the person via injection into vein
in vivo
- the new gene is inserted via a vector (virus/ liposomes/ plasmid) into cells inside the body

Question 23

Why are viruses the most commonly used vectors?

Answer 23

• they have mechanisms needed to recognise cells

- and deliver the genetic material into them

Question 24

What causes SCID?

Answer 24

• severe combined immunodeficiency is caused by the body’s inability to produce adenosine deaminase enzyme (ADA) which is the key to the functioning of the immune system
• without the enzyme, children die from common infections and is often isolated

Question 25

What are the genetic diseases that are treated using gene therapy?

Answer 25

- SCID (severe combined immunodeficiency) | - inherited eye diseases

Question 26

What diseases are genetic screening used for?

Answer 26

- breast cancer (BRCA1 and BRCA2) - Huntington's disease - cystic fibrosis

Question 27

Describe how SCID is treated using gene therapy

Answer 27

- via ex vivo somatic gene therapy - a virus transfers a normal allele for ADA into T-lymphocytes which were removed from the patient - the transgenic cells are grown in the laboratory and then returned to the patient's body via an injection into the vein - it is not a permanent cure as T-lymphocytes are replaced - therefore, patient requires regular transfusions every 3 - 5 months to keep their immune system functioning

Question 28

Which vectors are used in the treatment of SCID using gene therapy?

Answer 28

- retroviruses were once used as vectors however it insert their genes randomly into a host's genome which means they insert the gene into another gene or into a regulatory sequence which could result in cancer (leukaemia) - lentiviruses or adeno-associated viruses are used - lentiviruses randomly insert their genes, however they can be modified to not replicate - adeno-associated viruses do not insert genes into the host genomes, therefore genes are not passed onto daughter cells when cell divides (problem only for short-lived cells)

Question 29

Describe how inherited eye diseases are treated using gene therapy

Answer 29

- leber congenital amaurosis is a group of inherited eye diseases that causes blindness due to damage to the light receptors in the retina - no cure for these diseases - treat using in-vivo somatic gene therapy - doctors inject adeno-associated viruses that contained the normal alleles of one of the genes that caused damage to the photoreceptors - (at least 18 known mutated genes causing this group of diseases)

Question 30

State the uses of genetic screening in medicine

Answer 30

> allow people with a family history of a genetic disease to have DNA analysed to determine if they're at risk > carry out pre-implantation genetic diagnosis (PGD) - embryos that are created outside the body with IVF have their DNA analysed - allows embryos that are not carrying a harmful allele that would cause the disease to be chosen for implantation

Question 31

State the use of gene therapy in medicine

Answer 31

- used to introduce corrected copies of genes into patients with genetic diseases - cystic fibrosis, haemophilia, SCID

Question 32

State the social and ethical considerations for genetic screening

Answer 32

> being able to take preventative measures - elective mastectomy when BRCA1 and BRCA2 are detected - give individuals control to prevent illness > pre-implantation genetic diagnosis to select embryos that do nor carry fault, disease-causing alleles - lead to fear of "designer babies" being created - diagnosis via IVF: cells are extracted from the embryo in an embryo biopsy and genetically screened in order to preselect the embryos without faulty alleles > Using genetic counsellors to help people understand their choices and make informed decision - financial costs, whether termination of fetus is appropriate if quality of life is poor > Risk of miscarriage (which has emotinal consequences) due to the procedures used to collect DNA which are not 100% risk-free Amniocentesis – is used to obtain a sample of amniotic fluid using a hypodermic needle at 15 to 16 weeks of pregnancy Chorionic villus sampling – is used to obtain a small sample of the placenta using a needle between 10 and 13 weeks of pregnancy > Choosing to terminate a pregnancy (therapeutic abortion) because the embryo has a genetic disorder - minor ‘defect’ that could have seen the child lead an almost normal life > Being able to make informed reproductive decisions > Determining whether it is best to know the risk of having a disease - even when no cure (Huntington's) > Confidentiality of the data collected - who will have the right to view the results obtained

Question 33

State the social and ethical considerations of using gene therapy

Answer 33

> potential for side effects that could cause death - the children who were treated for SCID developed leukaemia > Whether germline gene therapy (the alteration of genes in egg and sperm cells which results in the alteration being passed onto future generations) should be allowed - it could be a cure for a disease, or it could create long-term side effects > The commercial viability for pharmaceutical companies - if it is a rare disease, the relative small number of patients may not mean that the companies will make a profit > The expense of treatments - as multiple injections of the genes may be required if the somatic cells are short-lived (SCID) - make the cost of gene therapy accessible to a limited number of people > people will become less accepting of disabilities as they become less common > Who has the right to determine which genes can be altered and which cannot > Another method of enhancing sporting performances unfairly through gene doping - give unfair advantage